Lan bị mất ví trên xe buýt, nhưng trong ví không có nhiều tiền mặt.

Bị often marks something negative, unwanted, or unfortunate that happens to the subject.

So Lan bị mất ví suggests that losing the wallet was an unpleasant event for Lan. It often feels a bit like:

• Lan had her wallet lost
• Lan lost her wallet in an unfortunate way
• sometimes even Lan had her wallet stolen, depending on context

In everyday Vietnamese, bị is very common when talking about bad experiences.

Both are possible, but they are slightly different in feel:

• Lan mất ví = Lan lost her wallet
• Lan bị mất ví = Lan unfortunately lost her wallet / Lan had her wallet lost

Adding bị emphasizes the negative impact on Lan. It makes the sentence feel a little more like an unfortunate incident, not just a neutral fact.

It can be ambiguous.

Mất ví can mean:

• she accidentally lost it
• it went missing
• it was stolen

With bị, the sentence highlights that this was bad for Lan, but it still does not clearly say whether she dropped it or someone stole it.

If you want to be explicit about theft, Vietnamese might use something like:

• Lan bị trộm lấy mất ví
• Lan bị móc túi mất ví

Trên xe buýt is the normal way to say on the bus.

In Vietnamese, trên is often used for being on a vehicle:

• trên xe buýt = on the bus
• trên tàu = on the train
• trên máy bay = on the plane

Using ở xe buýt would sound unnatural here. Ở usually means at / in / located at, but for riding a bus, trên xe buýt is the natural choice.

Trong ví means in the wallet.

Vietnamese often puts location expressions before có / không có. So:

• Trong ví không có nhiều tiền mặt literally feels like
• In the wallet, there wasn’t much cash

This word order is very natural in Vietnamese. It sets the location first, then says what exists or does not exist there.

Yes. Trong ví and ở trong ví can both mean in the wallet.

But here, trong ví is shorter and very natural. Adding ở is possible, but not necessary.

Compare:

• Trong ví không có nhiều tiền mặt = very natural
• Ở trong ví không có nhiều tiền mặt = also possible, slightly more explicit

Both are possible, but they are not exactly the same in tone.

• không có nhiều tiền mặt = there wasn’t much cash
• có ít tiền mặt = there was a little cash

The version in the sentence focuses on not much rather than a little. That matches the English idea very well.

Also, không có nhiều... is a very common pattern in Vietnamese:

• không có nhiều thời gian = not much time
• không có nhiều người = not many people

Tiền mặt means cash, meaning physical money like bills and coins.

It does not mean money in general in every sense. For example:

• tiền = money
• tiền mặt = cash

So in this sentence, it means there was not much physical cash in the wallet.

Ví can mean either wallet or purse, depending on context.

Vietnamese does not always make the same distinction that English does. So ví is a general word for a small personal item used to carry money, cards, etc.

If context matters, Vietnamese can be more specific, but ví by itself is very common and flexible.

Nhưng means but.

It connects two clauses:

• Lan bị mất ví trên xe buýt
• nhưng trong ví không có nhiều tiền mặt

Vietnamese uses nhưng much like English but. It usually comes between the two clauses, often after a comma in writing.

Vietnamese often does not use possessive words like her when ownership is already obvious from context.

So Lan bị mất ví naturally means Lan lost her wallet. Since the wallet belongs to Lan in the situation, Vietnamese does not need to state của cô ấy.

If you did add it, it would usually sound more explicit than necessary.

Yes. Xe buýt is the standard and very common word for bus.

It is a borrowed form ultimately related to bus, but fully normal in Vietnamese. You will see and hear it all the time.

Yes. Trong ví không có nhiều tiền mặt is a complete clause.

Its structure is:

• trong ví = in the wallet
• không có = there is/was not
• nhiều tiền mặt = much cash

So it works on its own, and in the full sentence it is simply linked to the first clause by nhưng.