When you reboot you go back to the usual memory device you were using before the mount. The bubbles do not go anywhere before or after the mount. I have yet to refresh database btw. Ive probably rebooted 3 times and unmounted umao 10x around now. Everything seems normal atm.
You are trying to simply transfer a file from PSP to Vita right? Maybe this would help you... While adhoc is a no-go FTP should be good for transferring files.
http://wololo.net/talk/viewtopic.php?t=9689
What was the file extension originally?
If it was ".7zip", or ".rar" then extract it.You should see a .vpk or .zip inside.
If it was ".zip" then I assume rename the extension to ".vpk".
Btw its jpn not "jap".
"Use the MaiDump tool itself. Copy the game folder to uxo/mai, access the App and select the 2nd option (Install from folder)."
-bennnzx