Try to go to your Mnagaer data folder and look for subfolder with gibberish names in it.
Then in those subfolders there migh be file with 0000…0000 name, it might contain data with you transactions (see discussion => click).
Copy that 000…000 file elsewhere, rename to something like tst.bak and try to import it.
If there are several subfolders with gibberigh names, that means you have several businesses, try one after another to find one deleted.
It seems that Manager leaving data file after business removal (i.e. it is removing only data from index file).
Best