If the UN wasn't willing to fight then the best option was not to disarm the Bosnians but instead withdrawal and let them fight it out. At least the Bosnians will take some of the enemy with them.
As a part of the agreement on demilitarized safe zone (cue: demilitarized) Bosnian units were disarmed. And the soldiers did not go anywhere. The area was deep inside the Serb territory, so it was hardly possible for them to leave. Only a few of the commanders (notably, Naser Oric, the commander of the unit in Srebrenica was 'evacuated' by helicopter sometime during May, I think.