What would make a JFET in a Millenium Bypass die?

[sfr]

Here's an odd one - quite some time ago, I built a PT-80, following the board layout and info at General Guitar Gadgets.  I etched the board from GGG, and it includes a Millenium Bypass within the schematic. 

A little while ago, the LED stopped working, whilst everything about the bypass and the pedal functioned normally.  Removed the board from the enclosure and made sure nothing was shorting out - still no dice.   I suspected some of the offboard wiring to the switch - but it checked out fine.  I unhooked the LED and tested it, and it was fine.  The diode, too.  Ends up the JFET (A 2N5485) simply stopped working - replacing it fixed everything. 

The voltages out of the two regulators seem fine.  I haven't come across any shorts (although the problem may very well be intermittent  - I went through and tried to tidy the wiring up inside) and nothings jumping out at me as I check things over. 

Perhaps it was just a solder joint that went bad because the board got flexed, or it got banged around (because I often leave the pedal board in the back of the car for days...)  or just a fluke.  I'll see if it goes bad again. 

But I'm wondering, what would make a JFET just stop working in a situation like this?


EDIT: it occurs to me I can't remember if I actually checked the JFET after I pulled it to see if it had died, or was just a bad connection.  I reflowed the joints with no luck, which points to the first; but I really should have tested it out of circuit.  I'll have to see if it's still sitting at the bottom of the trash bin in the shop.