[quote user="ucDude"]BeagleBone IOs are not 230V AC tolerant ;-)[/quote]
Nor are the I/Os of just about any MCU presently known to man...
Unfortunately - while your introduction of, "out of spec" input signal was extremely severe - such, "Whoops! Signal introductions" are not especially uncommon.
A proactive method - which our group long has used - employs a separate, I/O "safety board" which is imposed between the MCU and the external world signals. This board is voltage/current limited - may even employ isolation or opto-coupling to prevent such, "unfortunate, MCU signal introductions!"
Yes - there is a cost associated - but such board can be "deleted" from the final/production bom once the safety of each/every input signal - over time - has been well established. There is also a time/cost/effort penalty caused by such unfortunate signal introductions - which may slay the MCU as well as multiple, other components. And - if you're especially unlucky - unexpected, elevated voltages may harm expensive test equipment and/or even personnel. And then - just what have you, "saved?"
We now always use such, "Safety" boards - and can report the incidence of such "disasters" has near vanished...
An ounce of prevention...
