virtualbox.org

Hi, I had a machine with a snapshot, I detached the disk and connected it to another machine, booted and made some writes to it.
Is there any chance I lost some data?
(I also changed some partition sizes of the disk)

What was "the disk"? The entire snapshot chain makes one disk with multiple restore points.

If you mean that you detached the base disk and wrote to it in some other VM, then yes, that could cause data loss, the importance of which can only be measured when you find out what's left. Resizing a partition would be just about the worst thing you could think of to do. And I don't suppose you made a VM backup first?

If you attached some other file (not the base VDI) then I need to know.

Note that, as mentioned, snapshot VDIs are not stand alone - they form a chain. If you moved one of the links (other than the base) to a new VM then it only worked because the other VM was still present, still registering the parent (earlier) links.

When did you last make a backup of this VM? Individual elements of the snapshot chain might be restored if you have any backups made after that element was frozen, i.e. after any later snapshot element was created.