RELAX...her vital parts don't wear out...she didn't give them away on a permanent basis...she just loaned them out for a short time and now you have them back. Hopefully some lucky guy or couple got to enjoy your wife's body that night. She was probably thinking you would be upset if she told you the truth about it.
Learn to go with the flow and you may find your wife's sexual escapades as erotic and enjoyable as I find my wife's. I actively encourage my wife to go out with her girl friends and to be a hot wife while she's out...I even provide condoms in her purse in case she gets lucky. It is a real turn on when she takes me up on it and returns home well used! Whenever she's successful I tell her to make sure she always gets the guy's phone number and/or email address...that way later I can try to get a MFM thing going with my wife and her new stud or studs.
Only thing I always ask her is that for her own safety she keep her girl friends close buy and if possible even have them in the same room with her and the studs...just in case she was to meet a weird-o who might be into hurting women. There's safety in numbers.