Mine did exactly this while I was out avoiding the royal wedding last week. Driveside chainstay snapped halfway thought, but held together as I limped back to the car.
I used it as am excuse to go shopping for sexy Ti, but also welded it back up last week (cos I can do it for free) and I’m now waiting to get it back from the (free) powdercoater this week. Then it’s getting all the bits off the Inbred swapped over to it as a second\winter\trailer bike. The weld looks good, so it should hold up fine.
If not, I’ve spent no extra money on it, so nothing lost. If it lasts, then I’ve saved about a ton in weight over the inbred frame and sexied the spare bike up a bit…
My frame was old enough that I didn’t bother pestering Cy about it – it’s done it’s duty well.