2 databases lost all data

I have been working on 2 data bases , building queries from tables and creating forms.
My OS is LInux Mint 21.0
LibreOffice version is 7.3.7.2
HSQLDB version is 1.8.0.10
I saved both base files as *.odb
2 base files just went to 0 bytes with no data showing in the tables.

1 of the base files has now returned to it’s original 3.6mb size, but the date field has changed from DATE to Text(VARCHAR), and I can’t change it back Another is still showing as 0 bytes, even though it has the data in both the tables and queries

Perhaps I should also mention that over the last couple of days whilst I was working on both base files, I was getting the file recovery box up several times,. I wasn’t aware that the said files had crashed as they were still useable.
Ok a strange thing happened. While both databases were 0 bytes, I opened them with LibreOffice base and the data has reappeared in both the queries and the forms
But the date format has changed from
Thanks

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