Ooh. We do love a bit of intrigue.
The good news is that for a sizeable-but-not-ridiculous service cost you will end up with an immaculate serviced watch that is documented and paperworked and kosher with Omega. In some ways that's better than the way it was when bought.
Obviously the down side is that someone has told you porkies and probably inflated their sale price through nefarious means. Bad form.
I would see what the person you suspect of mischief has to say - privately - and if they continue to dodge and weave then name and shame.
I'll sharpen the pitchfork just in case.