Am I the only one who is shocked that the OP thinks a 13 year old was with friends at IHOP until 2:00 am??? OP is assuming there are other 13 year old kids out to 2 on a regular basis, I just have not seen that happening anywhere I have lived (as an adult, or teen). OP, either she has a very unusual group of friends, is hanging out with MUCH older friends, or that was not who she was with. I am guessing the latter. I hoep she might have been hanging out more or less alone just waiting to be late enough to upset you, and not getting into serious problems though.
I tend to agree with most of what is said, so I will try not to repeat much.
OP, I commend you for being honest about your feelings. Nothing good comes from lying to yourself. You were very young when you married, and apparently super naive and assumed you could marry a man with a child and not have that child be a major part of your family. And, if you went assuming she was never going to live with you, etc, then CLEARLY at that time (and it sounds like for many years afterwards) she was NOT trated like family and not included in the way her father should have made sure she was.
So, now you are coping with a teenager (often hard in the best of situations), with four little ones in the house (making it a little harder yet) and a husband who travels often (even harder, I know all too well. mine travels 35 to 40 weeks a year). AND you have YEARS of her not being part of the family and feelign hurt and left out and the family foirming routines and habits which do not include her to make up for on top of all that other stuff.
Therapy woudl be a good start. Dont just think about it. Go! Drag your husband too.
And, sending her back to her mom needs to be 100 percent off the table. Either she is a child in your familz, in which case you work out problems as a family, or she is not. But she should no more live under teh threat of being sent away to her moms than the little ones should live under the threat of being sent to foster care for misbehaving. You do not throw minor aged children out when the going gets tough.
The only exception would be if thigns are truly dangerous, like drugs, very violent behaviour, etc, in which case, just as you would for the other children, you fins proper in patient care for the child to be safe, maintaine safety and home and HELP your daughter.
I agree with the person who would have put four cranky, tired kids in the car and and gone out looking, and had I not found her pretty soon put a call into police. If one of the little ones were very ill in the night, ill enough that you would take them to the ER if it were only that child at home, I assume you woudl still take them to the ER if it meant you had to haul all the kids with you, or call a firend in teh middle of the night to come watch teh other ones. This situation had just as much potential to be dangerous, and you needed to put the needs of the child in danger first, and go find her.
I also agree that groudning her for the time being, and rethinking curfew are in order (I never had a curfew and niether do either of my teens, we talk about hteir plans and decide on a case by case basis, but >I know where they are and when they will be back and they call if something comse up and they are running late. 2 a.m. and no idea where they are? no way!).
I do not think that totally unrelated consequences (like a book report) do anythign other than send the message that you are pissed off and in a power struggle (and make life harder for english teachers, since you have now set up school work as a punishment).
Hopefully some sort of family vounseling can help you and your husband come up with appropriate rules and consequences that you can both communicate to all of your children adn trhen both follow through on as needed.
good luck.