My thoughts

a) the attack on the Invincible may be what caused the demensional gateway/whatever.
b) Kei may be the one Gil sent his message to (as a core member of the WDF, there's probably a large Genom bounty on her head at this time, hence hiding in a nebula)
c) if the dimensional gateway was opened from the UF side, it could have been used to send a GENOM HK ship through in search of Gryphon
d) Gryphon and crew are probably keeping a low profile partly because he doesn't know how strong a grip Largo has on the UF-verse or what has happened since he left.