Rick the link below should give you the information you need about MLB holograms. As for Steiner, I have no idea as to why they no longer have an online database to look up hologram numbers but I'm sure someone here has an answer to that. I personally think in this day and age that it's an important part of my purchase to be able to look up my item to add that piece of mind.

One recent purchase of mine left me scratching my head. I purchased a flag that was flown at the old Shea Stadium from a Licensed Steiner Vendor. Upon receiving the flag which was shipped directly from Steiner's warehouse I realized there was no hologram and no paperwork. The seller contacted Steiner and I had a COA in a weeks time. So now I have a COA for a flag but how do I prove it is for my flag if I go to sell it without any hologram? I wanted to share this story because I feel a company as respected as Steiner should hold themselves to a higher standard.

So to answer your question... holograms are tamper proof and can not be transferred from item to item without being destroyed in the process. This goes for both MLB and Steiner holo's. Also, with Jeter game used items from Steiner you usually get a hand signed by Jeter COA.
http://mlb.mlb.com/mlb/authentication/hologram_info.jsp