irf3205, did i kill it?
So, based on your comment, and your as-yet-unknown circuit that isn't the one you posted a picture of, even if it's similar on the right side, you discovered the joys of gate charge on MOSFETs; where not connecting the gate can leave you with an active, conducting MOSFET since there happens to be voltage on the gate, and being a MOSFET, that voltage isn't going anywhere in a hurry (leakage might pull it down over a few weeks, or sooner if you put your finger on it.) 

I strongly suggest some active playing with a simple MOSFET - resistor - LED circuit if you don't have this one well-ingrained in your head. 







simulate this circuit &ndash; Schematic created using CircuitLab

Connect the gate, briefly, to + or - and then disconnect. Observe behavior. Turn power supply off, go to lunch, come back, turn power supply on, observe behavior. Learn that you need to actively shut a MOSFET off, as well as turn it on. The above circuit is assuming the more-common enhancement mode MOSFET which is off when the Gate-Source voltage is 0V.

The good news would be that you evidently haven't killed your MOSFET, and perhaps you learned something, too.