
While it is true that Forms can be hidden in the Navigation Pane, the attribute setting is "Hidden", not "Visible". And that property would be the same in any copy of the accdb FE. The OP indicates a second user's copy doesn't have the same problem.
It is possible that the OP managed to change the Hidden attribute in the original accdb before the split, then turn it on off again in the copy provided to another user, and then on again in the OP's own copy afterwards. Still that scenario needs to be fully fleshed out before we reach a conclusion.
We don't yet know if this is actually the problem the OP is experiencing because the description doesn't clarify what it means to say "the forms do not appear".