Wasn't it a group of Libyans who eventually managed to retrieve his body, and took him to the hospital? Maybe while the state dept employees are trying to save Stevens, these people (or people like them) help out and successfully retrieve the ambassador from the burning building in time. Could that work?
I'd have to dig the book out & review the time of each event. I dont remember how long the guards & others inside the wall were pinned down while the building burned. I do recall just from the guards testimony Stephens was problably beyond resucitation 40 to 50 minutes after the start of the attack.
I do recall clearly a portion of the guards were assigned to the "Annex" a CIA station outside and approx a kilometer \from the State Dept compounds wall. That split the guards into two locations.
A alternate WI to your proposal is if the SD station had been upgraded in name to a actual consolate or embassy status. In that case there would have been things like fire fighting equipment in the building, including masks & air tanks in or near the sleeping quarters. The buildings attacked have been frequently refered to as a "embassy", but it was not. It was a collection of low level State Dept offices and CIA offices, with some communications equipment. It was a place where Lybians could come to receive or turn in document for doing official & comercial business with the US, or where the intel Lybians gave was given its intial analysis & sent to the next level. It had no provisions, including appropriate communications for hosting a ambassador or consul. Stephens knew that & should have known sleeping over there instead of returning imeadiatly to Tripoli was a high risk decision. The guards indicated in their book Stephens could have flown back that evening, & was scheduled to do so in the morning with no further business in Benghazi.
Perhaps Stephens decision was based on the lack of any serious or significant hostile action against the SD/CIA offices in Benghazi? The book did not comment much on threat intel or indicators. That may suggest the security group found little threat, or something else. I cant say.