Sucks you lost him.. pretty sure I would of been no help. Everyone gives just as good of advice as I can I learned from them! Pulling on the stinger may have irritated it.. also hear mixed opinions on Mela/Pima with rays.
Pretty strange, first time Ive heard of a ray being lost by another rays stinger.. From what I understand they are immune to the venom and usually with patience they work themselves out. I wonder if it hit a vital organ or something like that? internal bleeding? Who knows.. I've seen random stingray deaths only to have the necropsy reveal huge chunks of splintered driftwood spearing outward from their guts into other important body parts.
Interesting theory about ingestion/pushing it out Mike - seems very likely.
Was the ray stabbed in the middle of his back like your other big ray gave him a good 'over-the-top' tail whip? Thats strange, too..
Well I am sorry I wish I could of helped and sorry I wasnt around I worked 15 hours today hooray I even sold a goldfish! but yeah it's too bad for your loss.. don't get rid of your rays tho, get rid of the polys. Rays are best for personal insight and growth.