I assume you are looking at the folder where it was - Desktop? maybe and entering Time Machine.
Rather than digging through the folders in your ext drive "backup:backupdb"...
Was Filemaker and the database left open for a month? Letting the machine sleep and never using "Save As"?
There are reasons not to rely solely on TimeMachine - http://www.macworld.com/article/1155441/timemachineallyouneed.html
Depending on the OSX version and TimeMachine version, the open file MAY not be backed up - exclusions in Time Machine preferences in System Preferences is where these settings are set.
Trying to recover a trashed and emptied file in Mac OSX is painful and often fails.
This is the best Time Machine info site I have found http://pondini.org/TM/5.html
Sorry, I can't help with your current situation but I have some ideas for the future. A couple of months ago a friend lost 5 years worth of work. It made me rethink my backup strategy. I now use a couple of drives as clones with one off site. Next, I use CrashPlan.com for cloud storage backup. My first priority backup set is a group of databases that are backed up every 15 minutes to the cloud. The software will even back up the file if it is still open. There are a lot of options on backup frequency and how long files are stored. If you need an older copy of a file, it's easy to go straight to that file, select the dated version, and download it. It gives me a lot of peace of mind. Oh, and you have the option to upload files with 448-bit encryption. There are lots of cloud storage options out there. Google around for them.
Keep in mind that using a connected hard drive for something like TimeMachine is not back up it's redundancy. And, anything left on site is vulnerable to fire or a smash and grab burglary.
Thanks for the answers. I guess I have a lot of data entry catch-up to do. And some additional backing up and saving to do.