Maybe the ant bridged the pins and died causing a faulty input/output logic that caused the high power device to be powered to long, overheat and melt solder. It could also have been dead some time but damp air absorbed into it's body made it conduct.
I have seen a working PC stored in the loft for a few weeks fail to boot properly when removed and powered on. The accumulated dust on the internals was fine when PC was used daily (probably overheated the thing slightly) but storage in the loft had allowed the dust to get damp and cause problems. A quick vacuum out and it started working again.