You just have to do a search and look for the date of the last modification which should be there if you click view and details when you are looking at the list.
Normally it is under documents / quicken but that can be easily changed at any time and one that old I am not even sure where it would default to. But it should have picked it up the way it always does if the file was still there.
Have you been creating regular backups? Things like these are the reason that quicken is always nagging you to create a backup file. And to upgrade every 3 years because the modern versions do a much better job of it even creating their own backups when you don't.
Quicken normally only uses 1 data file. You may have been doing something a year ago that caused it to make extras that were sitting around. If that file got deleted it might be in the recycle bin or you might be able to find it using a standard un delete program like this one
another possibility I have run into a couple of times is that somebody had a flash drive in the computer or floppy disk or rewritable cd and they did not realize that they had been running the quicken data off that drive for months and took it out one day and the quicken had no data the next time they used it.
The last possibility is that you have the correct file or it is just being sorted incorrectly and so the data looks old.
-Sorting the register-
Click on the account actions button on the top right
select sort / by date
In older versions that option will be under the view menu
Or there is a title bar on top of the register columns that says what is in the columns underneath it. Clicking on anything in that title bar will sort it on that column
If you click right where it has the actual word "Date" above the date column that will sort it on date. Click once to sort one direction twice to sort the other direction.