my musescore 4 crashed when I had a score I had just made and didn't save while i had another open in a different window, i closed both and it would usually say that it crashed unexpectedly, but it didn't and now my score is gone. What do I do?

If it was an existing score, then you can just reopen it and MuseScore will use the auto-save version if present.

If it was a newly created score, then you might be able to find an auto-save version called new_project.mscz in MuseScore's data folders, for which the location depends on the OS:
- macOS: in Finder, press Cmd+Shift+G and enter ~/Library/Application Support/MuseScore/MuseScore4
- Windows: in Explorer, enter the following in the address bar: %LOCALAPPDATA%\MuseScore\MuseScore4
- Linux: ~/.local/share/MuseScore/MuseScore

If this folder contains indeed a file called new_project.mscz, then this might be an autosave version of the lost file. Open it, and immediately save it to a safe location using "Save as…", so that you won't lose it again.

Same thing just happened to me! It is my first time using MuseScore and I was working on my score for 1.5 days. I had somehow assumed, it was saving my work behind the scenes periodically and I didn't hit Save. Now my entire work is gone! The temporary file is not in ~/Library/Application Support/MuseScore/MuseScore4. Arrghh! MuseScore should fix this such that the temporary file cannot disappear!

Ah, the annual score purge. This exact thing happened to me, and my score is nowhere to be found. All I did was press Ctrl-Z, and it closed unexpectedly. There is no trace of it. I worked for three hours on that score this afternoon.