sitagaki wo hozonsita tumori datta noni, kiete simatta.

下書き means draft.

In this sentence, it refers to something like:

• a draft of a document
• an unsent or unfinished text
• a draft version of writing

So 下書きを保存した means saved the draft.

The particle を marks the direct object of the verb.

Here:

• 下書き = draft
• を = marks it as the thing being acted on
• 保存した = saved

So 下書きを保存した means saved the draft.

Because つもり often follows the plain form of a verb, and the tense of that verb shows what action the speaker believed they had done.

Compare:

• 保存するつもり = intend to save
• 保存したつもり = believe/think you saved it

So 保存したつもり means I thought I had saved it or I was under the impression that I saved it.

The past form した is important because the speaker is talking about an action they believed was already completed.

Here, つもり means the belief / assumption / impression that one did something.

Many learners first see つもり as intend to, and that is correct in many cases. But with a past verb, it can mean:

• thinking that one did something
• being under the impression that one did something

So:

• 保存したつもり = I thought I had saved it
• not necessarily I intended to save it

This sentence is about mistaken belief, not just intention.

つもりだった makes the whole thing past: I had thought / I was under the impression.

Breakdown:

• 保存したつもり = the belief that I saved it
• だった = was

So:

• 保存したつもりだった = I thought I had saved it
• literally: it was my belief that I had saved it

Using だった shows that this belief existed before the speaker realized the draft was gone.

のに means something like:

• even though
• although
• and yet

It connects two ideas that clash with each other.

Here:

• 下書きを保存したつもりだったのに
• Even though I thought I had saved the draft...

Then the unexpected result:

• 消えてしまった
• it ended up disappearing / it was gone

So のに gives the sentence a disappointed or frustrated contrast: I thought I had saved the draft, but it disappeared.

しまった adds nuance.

• 消えた = it disappeared / it was gone
• 消えてしまった = it unfortunately ended up disappearing / it was completely gone

In this sentence, しまった suggests:

• regret
• disappointment
• something happening in an unwanted way
• finality or completion

So 消えてしまった feels stronger and more emotional than plain 消えた.

Because しまう connects to the -て form of a verb.

The pattern is:

• verb in て-form + しまう

So:

• 消える → 消えて
• 消えてしまった

This is a very common grammar pattern:

• 忘れてしまった = unfortunately forgot
• 壊れてしまった = ended up breaking
• なくしてしまった = accidentally lost

The subject is omitted, which is very common in Japanese.

From context, the thing that disappeared is the draft:

• 下書き is understood as the subject of 消えてしまった

So the sentence really means: I thought I had saved the draft, but it disappeared.

Japanese often leaves out subjects when they are obvious from context.

No. The sentence strongly suggests that the speaker believed they had saved it, but in reality something went wrong.

That is the point of:

• 保存したつもりだった = I thought I had saved it
• followed by のに = but / even though
• and then 消えてしまった = it disappeared

So the speaker’s belief was mistaken, or at least the result did not match what they expected.

Sometimes a sentence with 思った is possible, but つもりだった is more natural here.

Compare:

• 保存したと思った

  • I thought I saved it
  • focuses on what crossed the speaker’s mind

• 保存したつもりだった

  • I was under the impression that I had saved it
  • focuses on the speaker’s mistaken assumption

In this kind of situation, where someone believed they had done something but later found out otherwise, 〜たつもりだった fits very well.

Yes:

• 下書き = draft
• を = object marker
• 保存した = saved
• つもり = belief / impression
• だった = was
• のに = even though / but
• 消えてしまった = disappeared unfortunately / ended up disappearing

A fairly literal reading would be:

Although it was my impression that I had saved the draft, it disappeared.

A more natural English version is:

I thought I had saved the draft, but it disappeared.

It expresses:

• surprise
• frustration
• disappointment
• regret

That feeling comes especially from:

• のに = the result is contrary to expectation
• しまった = unfortunate outcome

So this is not just a neutral statement of fact. It sounds like: Ugh, I thought I saved the draft, but it disappeared.