Depending on how much info you have lost you could write python scripts to recreate 
issues, just created them as new. Usually you'd need all the other information that is 
not kept in the msg and file files, so it depends on your tracker.

Without the extra information that would allow you  guess the rest and create 
complete new issues and attach the "file"s and "msg"s you are lost though.
Sometime mysql keeps some logs or your can recover something of the broken 
datebases (depends on the mysql table type I guess).