What storage options have you specified for your container fields?
Where are your files located? On your computer or are they in a shared directory on a server?
I store them as "Store only as a reference to the file" and the files are located on my computer in the same file folder as the database. It always stays on my desk top in this folder. Sometimes I copy the entire folder to backup the database, but that does not drop the files.
That's not what I meant by storage options - a tab found in the field options for a given field can enable you to specify either global or external storage for a container field. Did you make any such choice for the fields where you are missing this data?
What do you see in the container field when it's inserted file "goes missing"? is it empty or do you see text with words that say something about being unable to locate the file?
The first indicates that something cleared the field? The second indicates that the file path stored in the field is not currently a valid path to a file.
I have not made that choice. They are both not checked. Not global and not stored externally. And yes when it is missing, there is text saying that it is missing.
So strange, they all just reappeared. That is the first time that has happened. Does that give you any clues?
Might you have more than one copy of your file?
Are you using more than one user account on your computer? (each has it's own desktop folder and the file path will thus differ with each user account).
Might your file be damaged? Run a recover on the file and see what is reported. Even if no damage is reported, test the recovered file to see if its behavior differs from the original copy.
And since filepaths are something that results in FileMaker interacting with the directories of your hard drive running a utility to check out your hard drive for issues might also be worth doing.