This doesn't surprise me at all. Years ago I had an ultrasound scan because my GP thought I had gallstones. The person who did the scan said that they thought I had gallstones, too, but they were small ones.
I since think the problems I was having at the time were stress-related anyway, rather than anything to do with the gallstones, as I had a truly awful boss.
Anyway, I didn't hear anything from the GP about the test and didn't think anything of it, as the stones were small and didn't need further action unless they were causing me major hassle which they weren't.
Six months later I got a phone call asking me to go to see the GP about my test result. I asked which test result. The gallstones one. I am a bit confused about this as it was six months before. Well it turned out that the hospital had sent my test results to the wrong GP who hadn't seen fit to forward it on, or send it back to the hospital. It's a good job it was nothing serious, I'd have been dead. I didn't complain but perhaps I should have done.
When you give blood they ask you constantly to confirm your name, address, DOB etc. Why on earth do they not do this in hospitals.
Anyway to cut a long story short - yes, complain - it's really serious. There's no excuse for errors like this. The NHS is wonderful, understaffed, underresourced - and needs to get rid of its witch hunt culture and put patients back at the heart of what it does. If there's an error, sort it out. Don't get all defensive and ignore.