Unfortunately, some of Logic's error messages aren't very helpful. IMO this message is (in some cases) both an example of a bug that shouldn't be there, and also of an error message that should have been worded differently.
If your song sounds OK after you've seen this message, maybe you don't need to worry, but I've had this message several times when Logic doesn't find the file it's looking for, but finds and uses another (and only one other) file instead. This may happen eg. if the external disk the original files are stored on isn't connected.
Depending on what kind of song it is, and depending on whether you're mixing your own or someone else's song, it isn't always possible to hear if wrong files are used instead of the correct ones. In either case, Logic should of course never replace a missing file with another file with different length (etc).
Another Logic issue related to this is that of Logic isn't finding the files it looks for, an option to either make Logic search for the file, or alternatively to locate the file manually is offered. The problem is that most people of course will see if Logic can find the file for you first, but if it fails, no dialog window appears that let's you manually locate the file instead.
I hope and trust that both these ancient issues will be addressed ASAP, but the could be a side effect of a much bigger problem: that not enough people who use Logic for real work are involved in (or listened to) in the Logic development process. Unlike some others, I think Apple mainly are good listeners, but this example shows that they should listen even more than they do, or listen more often, because AFAIK; these two issues problem has been around since version 1.7!
I know this thread is in the "Legacy versions of Logic" subforum, but I've had the problems I described above in 8.02.