The Elders Book says this about proof of fornication and/or adultery:
Strong circumstantial evidence, such as pregnancy or evi-
dence (testified to by at least two witnesses) that the
accused stayed all night in the same house with a person of
the opposite sex (or in the same house with a known
homosexual ) under improper circumstances, is acceptable.
So if 2 witnesses camped out all night on the same night and saw that the 2 of you "stayed all night in the same house" you are toast. Nothing need to have happened. This some how presumes that people do not have sex in the day time only at night and that it takes all night to accomplish the act. When does it become all night...if you left at 1 a.m. would you be safe...I don't know.