How to recover deleted files?
It's probably best to ask for advice on a support forum. Is it possible to recover a deleted file?
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Yes, but it's non-trivial and you should not be using the drive that the data was on at all. If you are using the drive normally there's a good chance that sectors containing your data will be overwritten.
To investigate getting the data back you should look at Photorec and testdisk. This use of these programs is a little beyond the scope of AskUbuntu but you should be able to find more information on their use easily.