Hi Philbil and welcome to GoY. Potting compost is for sowing seeds and cuttings not for a grown tree. Did you plant in the ground or into another pot? If into a pot and the compost was all the growing medium the fig tree had it simply wouldn't have been able to sustain itself.

Would it have died so quickly though MG? There's some plant food in most potting composts.

Not a heck of a lot though... wonder if it was watered at all, up until this cold spell it has been really warm and plants that have just been moved/repotted do dry out rapidly. Guess we'll need to wait until Phil responds.

Maybe it had been growing under glass and the move outside was too sudden?

Possibly - who knows...