Symbols are not always found in SAFE bookstore project

[cartermp]

Upon investigating #5521, I noticed that symbols are not always found for some things in the SAFE bookstore app.

I also noticed that finding symbols for Find Refs or Rename is inconsistent in this project. For example:

Wishlist/Msg:

Not a linked file, and the references live in the same file.

Database/DatabaseType:

Not a linked file, and all references live in the same file.

So linked files doesn't appear to have anything to do with this (although it also reproduces in linked files, e.g., Shared.fs/Msg)