Would you be mad if spouse went to happy hour and didn't tell you?

Generally speaking, any activity like that (happy hour) is a JOINT activity, if you care to maintain your marriage. She should not be going to happy hour without you. She can't even use the excuse that it is "girls night out". If she's married, then her husband is her number one priority and "the girls" need to deal with that...or not. But there's no such thing as activities outside of the home without your spouse.

The other issue...

Even if there is a valid excuse for a woman to go somewhere without her husband (like to work, for example), then EVERY SECOND that the two of them are not together, the husband needs to know

1 ) Where she is

2 ) What she is doing, exactly

3 ) Who she is with, exactly (and it should go without saying that she's not allowed to have male friends)

4) A darned good estimate of when she will be home. Let's say within 15 minutes, maximum. More than that requires another phone call.

Would I be mad if my wife went to happy hour and didn't tell me? No, I would be divorced. Not mad, just single...

No not wrong in wanting your spouse to let you know if they are going to be late because they stopped off for some drinks. To me its just common courtesy to do so.