Workbook in in VBE but not in Excel

[foxguy]

I have a workbook that shows up in VBE, but is not in Excel, neither hidden nor visible. It's one of the files that have a collection of macros. It's a file that is opened only on my computer.
In the VBE I can see all the modules, subs, functions, etc. I can run a sub, but when another workbook tries to access it, it can't be found.

This is not the first time this has happened. I'm pretty sure it has something to do with closing and/or opening files that have a reference (VBE, Tools -> References) set to another file.

Any idea what I may have done to get to this state?

[shg]

Is it an add-in?

[royUK]

Is it PERSONAL.xls(m)?

[foxguy]

Is it PERSONAL.xls(m)?
Is it an add-in?

It is not an add-in.
It used to be Personal.xls, but it has been renamed to Mine.xls, so I don't accidentally confuse it with a file that Excel creates.

It's one of 3 files that I keep in xlStartup.
File1 is macros that are distributed with ALL my workbooks, clients and personal. It does call File2 for some macros, but checks to make sure it is open 1st.
File2 (this one) is a file of macros that I keep on all my computers. It references file1.
File3 is a file I keep on my Desktop (where I do most of my work), primarily to add menu buttons for frequently opened files. It also references File1.

The problem arose when I closed File3, then File2, then File1 (so there are no workbooks open, but I didn't check the VBE to see if all were closed there). Then I opened a file that references File1 by mistake. It opened File1, and somehow File2 was opened in the state I described.