Was it hot? On my 91 if it's hot out my gauge will peg full, once it cools down or I shut the car off for the night in the morning it will be fine again,I'm 90% it's my slosh module acting up,just a hunch.
If your needle pegs all the way to full and it doesn't come down you have lost your float,I went thru 3 sending units, one from Mustangs Unlimited and 2 from LMR and all 3 floats disintegrated, had to drop my tank and clean it really good,bought a Spectra brand from AutoZone 5 years ago and never had that problem again.
The problem I'm having now that I mentioned it's my slosh module I think but once the weather cools down the sending unit works like a charm again,what Ive been doing till I get it fixed is when I first turn on my car I see where I'm at and put fuel in accordingly.