There isn't a dedicated support team, it is just volunteers and people of the Joplin community, I doubt anyone intentionally ignored you, posts just fall through the cracks sometimes.
Unfortunately there isn't much to go on. I don't think anyone has reported this before so it certainly isn't a common thing.
The symptoms almost sounds like a bad sync setup, as if it found a blank sync target.
Do you have any backups of your database or exports in JEX format?
If not then your best bet might be to try to recover the notes using this process (or at least see if anything still remains of them).