When a spare tire in that type of location is not used for an extended period of time, there is a tendency for it to stick to the underside of the chassis. Now that you were able to finally get the spare dislodged, I would suggest that you make it a practice to lower the spare at least a few times per year. When you lower it, you can check/correct the inflation pressure, as well as reduce the tendency for it to stick in place again.