I always seem to be on the verge of getting busted by the GF. Like the weekend I spent with my ATF...trying unpack before the GF got home. The time I had a nooner and my tie got in the way and it smelled like sex (my new favorite tie). After having a late afternoon session, coming home with the smell of her perfume still on me and giving the GF a hug and a kiss (changing the routine is always a dead give away). Texting my ATF in front of the GF (who would ever be so bold). Or when the GF said "I think you have been cheating on me", I responded with "is that a question or a statement", she said "it was a statement" (she didn't really want to know).
The key is not the smells, clothes, or disappearing...it's our behavior that they hone in on. When we act different or guilty the other signs just add to their suspicions. The difference between me and most guys, I'd let the GF blow me right after having sex with someone else and I could pull it off. Not giving them at least a peck when you get home is a sign of guilt. Since I'm not guilty of anything other than giving her a temporary reprieve from sex, I'm doing us both a favor (that's a sign I need therapy, more sex, or both).
If you are a good BF, SO, or Husband...they don't really want to know! I guess if I were married, I'd be more careful since I would have more to lose. The fact that I'm in the hobby means the GF is on borrowed time.