Hi FIB, I do trust my wife. In the rational, loving, "higher plane" parts of my brain and my heart, I don't think she is sneaking around and finding another OM, or anything else like that.
When I backslide and do the very occasional snooping, it doesn't help me (even though I find no incriminating evidence). I see it as myself failing, and then I dust myself off and try to do better next time. Rebuilding trust isn't easy, it's hard. It isn't all or nothing, it's baby steps and keeping your eye on the far-off prize.
If I understand your question, you are painting things very black and white here. Either my spouse was at one end of the spectrum (screwed up one single time while drunk out of her mind, who desperately wants to save our marriage) or at the other (a serial adulterer, who cares nothing about our relationship).
The truth is much more "shades of gray" than that. Her A wasn't the result a single night of drunkenness, it was part of a long and painful MLC. The relationship wasn't rosy before she started to walk away, it was rocky. The fault for that wasn't all hers, it was shared by me as well. We both have a lot of work to do to piece our marriage back together.
Thread #10 22 year M, MLC, Piecing since 1/07 Goal: Live with confidence & enthusiasm!