There are some reasons why they didn’t fly there:
The core part of the Libyan op was MANPADS to “rebels”. This shadowed the intervention pattern when the Russians were in Afghanistan. There were something less than 22,000 MANPADS floating around North Africa, particularly in Bengazi —a clear shoot-down risk.
There was probably even some worry that the attack had been initiated specifically to cause the on-scene arrival of one or more large US transport/rescue aircraft into an AMBUSH, in a kind of “Blackhawk Down” imbroglio.
There’s the possibility that the plan was a prisoner swap gone bad, but a darker one is that higher-ups sensed the sensitivity of a compromised Large-Scale Smuggling Operation and simply hoped for a time that everyone in The Annex would be killed, thereby keeping it quiet.
Can’t believe we aren’t able to rig the MANPADS. To not work against friendly AC. Back in the Cold War we rigged a bunch of telecom equipment sold to Poland so that in the event of war, it could be disabled and would have cut the Warsaw Pact com lines running through Poland. Surely we could do better against. A bunch of 7th century Mooselimb terrorists....