haven't looked at one in a while, but is there room to slip a small left handed drill bit in there ?
if so, you could try to lever it in with a bar ( dimple the bar with a slightly larger drill bit, so the l/h drill bit stays put) to put lots of pressure on bit, then turn bit with a pair of vicegrips until it bites and starts to cut. at some point during this the cutting should make the bolt back out...if you're lucky.
if so, you could try to lever it in with a bar ( dimple the bar with a slightly larger drill bit, so the l/h drill bit stays put) to put lots of pressure on bit, then turn bit with a pair of vicegrips until it bites and starts to cut. at some point during this the cutting should make the bolt back out...if you're lucky.