gabangeul ilheobeorilkka bwa bunsilmulsenteo beonhodo jeojanghae dwosseo.

Here, 잃어버릴까 봐 means because I was worried that I might lose it or in case I lose it.

This grammar is used when someone does something because they are concerned about a possible future situation.

So:

• 가방을 잃어버릴까 봐 = because I might lose my bag / in case I lose my bag

In this sentence, the speaker saved the lost-and-found center’s number as a precaution.

Both are possible, but 잃어버리다 is very common when talking about losing something.

• 잃다 = to lose
• 잃어버리다 = to lose, often with a stronger sense that it’s gone, misplaced, or lost unintentionally

So:

• 가방을 잃을까 봐 = in case I lose my bag
• 가방을 잃어버릴까 봐 = in case I end up losing my bag

The version with -어버리다 often feels a little more natural in everyday speech for losing possessions.

Because 가방 is the object of 잃어버리다.

• 가방을 잃어버리다 = to lose a bag

The particle 을/를 marks the thing being lost.

If you used 가방이, it would change the structure and sound unnatural here. The speaker is not saying the bag is doing something; they are saying they might lose the bag.

분실물센터 means lost-and-found center.

It breaks down like this:

• 분실물 = lost item(s)
• 센터 = center

So 분실물센터 번호 means the phone number of the lost-and-found center.

Depending on the situation, this could be a station’s lost-and-found office, an airport lost-and-found, a department store service center, and so on.

도 means also / too / even.

So 분실물센터 번호도 저장해 뒀어 suggests that the speaker saved that number as well, probably along with other useful information.

For example, the unstated context could be something like:

• I saved my hotel address, emergency contacts, and also the lost-and-found center’s number.

Without 도, it would simply be:

• 분실물센터 번호 저장해 뒀어 = I saved the lost-and-found center’s number.

With 도, it adds the nuance of also.

저장해 뒀어 comes from 저장해 두었어, often contracted to 저장해 뒀어.

• 저장하다 = to save
• -아/어 두다 = to do something in advance and leave it that way for later use

So:

• 저장했어 = I saved it
• 저장해 뒀어 = I saved it and left it ready for later / I saved it in advance

In this sentence, 저장해 뒀어 is especially natural because the speaker is preparing for a possible future problem.

뒀어 is the contracted spoken form of 두었어, from 두다.

The pattern is:

• 저장해 두었어
• contracted to 저장해 뒀어

This kind of contraction is very common in everyday Korean.

Some similar examples:

• 사 두었어 → 사 뒀어 = bought it and kept it
• 적어 두었어 → 적어 뒀어 = wrote it down and kept it there for reference

So 저장해 뒀어 sounds natural and conversational.

Yes. The final ending -어 / -았어 / -었어 here appears as 뒀어, so the sentence is in casual, informal speech.

That means it would be natural:

• with friends
• with family
• with someone younger
• in a diary or text message

A polite version would be:

• 가방을 잃어버릴까 봐 분실물센터 번호도 저장해 뒀어요.

A more formal written or careful spoken version could be:

• 가방을 잃어버릴까 봐 분실물센터 번호도 저장해 두었어요.

Yes, and that often confuses learners.

In Korean, -을까 봐 / -ㄹ까 봐 expresses worry about a possible situation, and the next action is usually a response to that worry.

So depending on context, English may translate it as:

• because I was worried that...
• in case...
• for fear that...

In this sentence:

• 가방을 잃어버릴까 봐
  can be understood as
  because I was worried I might lose my bag
  or
  in case I lose my bag

Both capture the meaning.

Korean often omits subjects when they are clear from context.

So this sentence naturally leaves out the subject, but it is understood as something like:

• 나는 가방을 잃어버릴까 봐 분실물센터 번호도 저장해 뒀어.
• I saved the lost-and-found center’s number too, in case I lose my bag.

In everyday Korean, leaving out obvious subjects is very normal and makes the sentence sound more natural.

Not really. The sentence means the speaker prepared ahead of time.

That is exactly what 저장해 두다 helps show: they saved the number in advance, just in case.

So the logic is:

1. I might lose my bag.
2. Because that could happen, I prepared by saving the lost-and-found number.

This is perfectly natural, especially for someone traveling, commuting, or being cautious.

A less casual version would be:

• 가방을 잃어버릴까 봐 분실물센터 번호도 저장해 두었어요.

A plain dictionary-style breakdown would be:

• 가방을 = bag + object marker
• 잃어버릴까 봐 = because I might lose it / in case I lose it
• 분실물센터 번호도 = the lost-and-found center’s number too
• 저장해 두었어요 = saved it in advance

The original sentence is just the natural spoken version of that.

Yes. This is a very useful pattern.

Examples:

• 늦을까 봐 일찍 나왔어.
  = I left early in case I’d be late.

• 비 올까 봐 우산 가져왔어.
  = I brought an umbrella in case it rains.

• 까먹을까 봐 메모해 뒀어.
  = I wrote it down in case I forget.

So your sentence follows a very common Korean pattern:

possible problem + -을까 봐 + preventive action

That is exactly what makes it sound natural.