I once happened along a sportive rider (I was just doing a DIY 200 on my own) who was struggling to fix a puncture - he was 150km into a 160km ride and was clearly exhausted - he'd changed the tube but then pinched it putting the tyre back on the rim so it he pumped it up it went again.
I patched the tube and pumped it up for him (whilst the rest of the sportive riders ignored his plight). When I went to put the wheel back in he couldn't find one of the springs for the QR skewer, at that point, I'd done all I could and had spent 15 minutes helping someone that was struggling - but I didn't have a spare spring and I left him to it.
Told him I wouldn't ride without the spring but you're 10km from the end - try it or walk...