Placing the watch in a strong magnetic field? It's a sure way to magnetise the movment and jam it for good. In fact, your watch may have been subjected to a relatively weak magnetic field diring those 5 years. That field, over time can magnetise the movment and prevent it from mooving. The gears are acting like magnets attracting one another.
The thing to do in that case is degausting. It use an alternative magnetic field that start relatively strong, then get progresively reduced to zero.
It's a delicate procedure, as if done wrong, it can very easily fry the electronic part. DON'T attempt it yourself. Ask a qualified technician.
In some cases, it may only be a mather of gently taping the watch against your hand.
Electro, October 2012