Yes, when I was out of town for Army summer camp in college I suspected odd behaviors from my girlfriend immediately upon return. I didn't catch them but knew something was up, so I called her out. She admitted to it, and asked forgiveness.
Due to complete lack of trust, I immediately started to pork my business finance tutor (meh), the chick in our marketing group (yum), and a co-worker from "The Buckle" that smelled GREAT. I continued to get a piece of ass from my girlfriend, but didn't trust her. It was completely over about 3 months after I returned from summer camp.
20 years later I was at an industry work event and saw a mutual friend of mine and the girlfriend. Apparently she regretted her actions, and said she fucked up and should've never cheated on me. So nothing dramatic like a red-handed gotcha, but if you pay attention behaviors will provide lots of insight. Glad it didn't work out as she could be outspoken to the point of making people uncomfortable.