God.
This reminded me of my youth running wild after being sheltered and introverted... At the time I was 13 and in urban america with lots of drugs but other than that, my perspective was identical.
Dealing with all the oddities of foreign travel, sleep deprivation, a budget, and just plain inexperience (and no one to trust who has that experience) would be devastating.
I'm surprised it turned out as well as it did for you honestly and if builds my theory that 90% of people that go to or that you will meet in Ibiza are nice, helpful, and basically good.
That said, there's still 1 out of 10 that will try to screw you over for fun.
On the spiking of a drink... It's not so impossible that you were saved by being slightly naive. I start chatting to a pretty german girl that seems willing to go the distance, I'm outta teh club in a flash. Your mate probably did not fall for that because it never would cross your guys mind to try to bang a hot german girl in the bushes outside a club... or a beach or in a cab, on a bus, between parked cars, on a parked car,... you get my point.
I've often thought that when I see a guy off his nuts sitting down looking smashed with some girl attending to him that it's teh perfect set up for her to be robbing the guy.
Who would ever think that she's not just taking care of her man who thought "well, this **** is weak..."
I picture a girl looking around to pull a young guy that might have looked naive and possibly carrying a lot of money away from his friends to try to rob them (it probably would not cost a lot to put a few drops of Rohypnol in a drink).
I also believe people sometimes do that just to f with people... I would if I was in suitable company to enjoy the show/joke... but I can tend to be a right bastard if I'm out with other right bastards.
Over all though, brilliant review and I think you have probably really learned a lot of very helpful things that should make your next adventure far less vexing.