A lot of people while they are drinking from a mug will hold it in their lap. In this case it is important to remember that at a bar probably does not mean the actual bar part of the bar. They were most likely seated at a table within the bar drinking coffee and talking to someone while holding their coffee because they were drinking it like a lot of people (mug in one hand, the other hand either resting around or next to the mug) do and then they were asked if they wanted a refill and the FML began. It's really not as weird as it sounds if you take the time to think about the various positions people shift through when they are simultaneously consuming food and beverage and socializing.

Coffee cups belong in the table. If you've no concept of table manners you shouldn't eat or drink in public.

In the table? That doesn't seem right. Plus how does one drink a beverage if it's only ever located on the table? It's actually considered really rude to bend down to the table to sip from your beverage, even if there is a straw in it. Think really hard, and think about it honestly rec_chem how often, be it soda, beer, coffee, whatever, do you see someone just holding their drink while they are talking to someone? They talk, talk, talk, take a sip, talk talk talk, talk, sip some more, talk talk talk, sip, a little more chit, still holding drink drink while getting distracted by the song over head, take another sip, chat some more and then return the drink to the table having now remembered that they are for whatever reason still holding it. It's because despite what you say, most beverages are meant to be carried with you. That's why so many have lids. We get into the habit of bringing drinks with us everywhere so when we are staying in one place we still feel the need to hold on to our drink. Plus in bar such as the OP was in, it is generally advised, that you don't set your beverage down or put it in any position that would allow a stranger to have access to it.