Ah yes, it was there. Like Ft Sumter, Ft. Pickens was part of a fort complex, and like Ft Sumter, the officer in command acted to protect his men from the insurrection.
If it was at Fort Barrancas, then the incident you are thinking of happened well before Buchanan's truce at Fort Pickens. A day or two after the incident you are thinking of, Union troops abandoned Fort Barrancas and moved over to Fort Pickens. This happened maybe January 10 or 11 (too lazy to look up the exact date).
The truce with Buchanan didn't go into effect until late January or early February, 1861. In late January, Buchanan secretly sent the ship Brooklyn loaded with troops with which he intended to reinforce Fort Pickens. This was much like his earlier secret effort to reinforce Fort Sumter with troops on the Star of the West. Florida troops found out the ship was coming and said basically we will attack Fort Pickens unless you stop the reinforcement. The truce that was then agreed to by both sides was to keep the status quo -- the Union would not reinforce Pickens and the South wouldn't attack it. If the Union tried to reinforce the truce, the South was free to attack the reinforcement effort and the fort. Pickens was a large fort, and the small Union force inside the fort at that time could not have adequately defended it from attack.