Sign blueprints in loot table?

I have not yet seen nor heard of anyone on the official server i play on getting a sign blueprint for the larger signs. Are they in the loot table?

Yep, 2 of my teammate loot the Bp.

Very hard to find. We play on a server of over 120 ppl average, and after 15 - 20 hours each, none of my crew have found any sign BPs. As far as I know, one large sign BP has been found on the whole server so far…