I'm attempting to refurb my old 3gs for a friend, and now it won't turn on.

I'm not new to jailbreaking. I did a restore to iOS 5.1.1 via redsn0w 0.9.15b3, then jailbroke it not via DFU (since it was a clean reformat, I didn't see the need). installed cydia, started researching unlocks, realized I had baseband issues (the phone has 05.16.05, and from what I've read, that meant upgrading to the ipad baseband so that I could downgrade to 5.13.04 and then unlock). I went back to redsn0w and clicked jailbreak again, this time yes to DFU, so that I could alter the baseband. I turned the phone off to be able to put it into DFU mode and now it refuses to turn on. doesn't matter if it's plugged into my computer, or plugged into the wall, or on its own, or normal power-on, or DFU power-on. it's a paperweight.

any advice? was telling it to jailbreak again in redsn0w really that bad of a call? (note that it didn't actually start the jailbreak before it bricked.)

device details: 3gs, old bootrom (serial xx920xxxxxx), iOS 5.1.1, baseband 05.16.05.
it did sit in a cupboard for seven months before tonight, so that might be why. maybe it doesn't want a new lease on life. maybe its done. doesn't seem to be a battery issue but perhaps some other aspect of the hardware has failed.

thanks in advance for any advice!