I'm a former AA member so I'm familiar with the 1 year rule. I've read the BB and all the literature. No, it isn't in there.
But the way I see it is: the Big Book is not the bible, or the repository of universal truth, and the question is not whether something is or is not in there (and, as others have noted, "don't drink" isn't in there, either) but whether or not the suggestion makes sense FOR YOU IN YOUR PARTICULAR CIRCUMSTANCES.
If you are someone who is not currently in a relationship, has had trouble with relationships in the past (particularly if you have been abusive in them, or are triggered to drink by them), then it is probably an excellent idea for you not to get involved until you get your act together. In fact, if this is the case, one year might not be long enough; that time period is completely arbitrary and in my experience, people who have relationship issues coupled with addiction tend to take a whole lot longer than a year to get their heads on straight.
Now, as to the person who told you to go ahead and have sex, but not get emotionally involved: that person is a jerk, to be safely ignored. Talk about not in the Big Book! That notion isn't in any reasonable moral code I ever heard of.