Time Machine has 'lost' backups

I last accessed my time machine on the 19th May and successfully recovered a file that was created on 15th May. Later that day I switched my External Time machine disk off.

Today, I've just gone into Time Machine (yes after turning my disk back on before you ask) and the latest backup is dated 4 May. I've checked the disk via Finder and sure enough there is nothing after 4 May even though TM ran normally between then and the 19th. This was vital as I've been working on a critical project.

Anyone any ideas how TM has lost files? Incidentally, backups from April and March are still there.

Any chance the external was switched off or unplugged without being ejected? Or perhaps was it removed without stopping the Time Machine backup process?

Have you tried running Disk Utility on the external?

If I were working on a critical project, I would probably leave the backup drive connected the entire time. This way, you'll be sure to capture all incremental changes.

What do the log files say ?

If nothing suspicious, launch a new TM backup and watch the logs in real time, it might be that TM needs to do a rebuild of its database.

Cheers ... McBie

Thanks cwa107 and McBie. Just to clarify the points raised. The project completed on the 19th and as I wasn't going to be doing anything other than surf the net I ejected the drive before turning off. Actually, thinking about it after ejecting the drive I didn't switch it off as today I just "reintroduced to the mac" (by pressing the encryption button - its a freecom hard drive pro).

This pm ran Time machine manually and it's now showing that there is backup timed at 14:05 today so I'll leave it on auto and see what develops.

Incidentally, mcBie, where do I find the log files?

Go to Applications/Utilities and launch Console.app

Select " All messages " at the top of the left window pane
IN the right window pane, the second column title says " Sender/PID "
Watch for messages coming from (backupd) and see what they say.

Have attached an indication of what you may be looking for.

Cheers ... McBie