But....it was a forward pass.
Sarries can be furious if they want, but if they'd have won because of that/a law technicality then it'd be the hollowest of hollow victories.
I've got no problems with the TMO asking if he wants the referee to check something, as the referee can't see anything, I see this as no different to a touch judge asking. I've seen before where a TMO has mentioned to a referee that there'd been foul play in back play, and they've gone and checked and seen it.
No idea if this is technically allowed (I imagine not, from the amount of winging coming from some fez heads) but it should be, imo.