Slip and nasty fall

Sorry to hear this, it could be due to a diesel spill. I sometime see vehicles that have been filled to the brim and then it as it turns a corner in the opposite direction to the side the filler is on, fuel leaks from the filler neck, and if it's diesel, doesn't evaporate. 

I was on a group ride once when about half a dozen of us came off simultaneously. It was May, the road was under trees, we think a huge amount of aphids on the new leaves had dripped slimy tree sap onto the road surface.
Got a dislocated shoulder out of that one.

Sorry to read that, hope you're back out again soon!  Sounds like you're an experienced rider and it was one of those things.

Salt ironically is certainly slippery, or maybe there was some diesel on the approach. 

After a dry period, there is a build-up of rubber and other debris which can be slippery when wet- this can be particularly bad in a summer shower on the Continent.

First up - wishing you a speedy recovery.

The same has happened to me. I don't know whether it is due to the physics of tyres being cold, old, or soemthing like that. My biggest suspicion is that, at this time of year, the roads have a LOT of runoff on them. Lots of bits of tiny gravel, road salt, etc, particularly if there has recently been heavy rain, like mini ball bearings. Just take it easy in the corners. 

I suspect the answer is to build the confidence back up - brake early for corners, relax into them, don't brake or accelarate in corners, get your centre of gravity lower and go on the drops. Relax, relax, relax, and avoid the "death grip" on the handlebars.

Of course, this is easier said than done.