OP, aibu is where posters come when they're having a bad day and want to put the boot into someone. It's the worst part of MN, and the worst of all of it is that HQ are proud of it.
It's very clear that people have deliberately twisted what you've written to suit their own agenda's.
It seems very clear to me that you brought up having been to the festival previously and the fact he went to London with his son as examples of the fact that you're obviously not controlling and preventing him from having a life, contrary to what some seem to think, and the fact that the last time you went to anything musical you slept through it because of your illness.
Added to which, if posters actually read the thread, they would see that the OP stated that the reason she didn't get involved in buying the tickets was because it was DH's friend and he'd said he would sort it.
I am absolutely not of the LTB persuasion, however, it does seem fairly obvious that your DH had no intentions of taking you to this gig, and that the ticket was most likely pre-arranged between him and his mates, given they all got to go together. My references to whether or not he might be feeling entitled to time out were based on the fact that if this does come up in discussion, he may well make that kind of claim.
You are absolutely not unreasonable to be upset. But I would have an honest conversation with him along the lines of: "look, it seems very obvious to me that you wanted to go to the gig and didn't want me to go, so why could you not just tell me that in the beginning rather than go with all this subterfuge around tickets and then no tickets and one ticket, the more complicated it got the more obvious it is that you didn't want me there." And then talk about it. If you generally have a close relationship then you should be able to talk about it without it blowing up into an argument, and what's done is done, but if there is some thought process in his head which means he wants to be doing stuff without you then you need to know what it is so you can talk about it at least.