It was soon after Miz won the title that I heard the guys on Chair Shot Reality talk about the briefcase that Alex Riley carries to the ring. They didn't say why he carries it, but they did express that the announcers should mention it to the fans that didn't know why A-Rye still had it. I think they (the CSR guys) said that the announcers should mention that it is not the MitB contract briefcase, and explain the purpose for him carrying it (in case the fans had forgotten).
I remember thinking "yeah, what the hell IS in that briefcase?", but soon forgot (or stopped caring). To be honest, I don't know if there was ever anything to "forget"; I don't remember EVER hearing about why A-Rye had a briefcase (unless you count the MitB case that he used to carry for the Miz sometimes).
I must admit that I think about what's in that damn case every time I see A-Rye on Raw now, but not enough to really search around. Now I'm curious enough to email the guys at CSR about it, and ask them. Maybe they'll have an answer for us? ...if/when they get back to me, I'll post the answer here.
Btw: I really like your theory, synnamongirl77. It is a little far-fetched, and is probably not what's really going on, but it would make for an interesting feud for when the inevitable Miz/A-Rye split happens. Welcome to the forums, as well!
EDIT:
The episode of CSR is (kind of) coming back to me now...I seem to remember them saying that the case was just the (now empty) MitB briefcase. At least that's what the hazy memory is telling me, but that doesn't seem to make sense...considering that the MitB case was red (or orange, or whatever), and A-Rye's current case is just a basic metallic silver with no ornamental paint or other aesthetic attributes...isn't it?
A-Rye's current case reminds me of the briefcase from the end of the movie Twins (haha!). If I remember correctly, the case in that movie was filled with $5 million. Arnold also had a similar case that he traveled with in the movie, just for his clothes. Maybe A-Rye is planning on buying a Cadillac with a nuclear reactor in the trunk.