NC for this. Long time MNetter, been on the site for years. Promise!
I went out last night with a friend and his brother and girlfriend. The friend lives abroad and is back for a few days so it was a nice chance to see him.
They had already eaten when I arrived (an independent gastro bar with table service) and then together we had a round of drinks before planning to move on to another bar.
We asked for the bill, which included the total of the food/drinks they had before I arrived and then the one round of drinks we had together.
When it arrived, friend said "let's just walk out, shall we?" Before I could even fathom what he meant, his DB and GF had agreed and they stood up and walked out.
I was completely 
and had to make a split second decision about what to do. The bill was large and I couldn't afford to pay it all - nor felt morally at the time that I should - I put the money on the table for my drink and left feeling mortified.
I am usually very assertive but I was just so shocked I didn't know how to handle it. I'm ashamed to admit it but I didn't call them up on it (they were all so cool about doing it) so en route to the next bar I feigned illness and came home.
It can't be a money thing, DF and his GF both have very good jobs, the brother is working.
AIBU to be absolutely mortified at being part of this? I feel that they have implicated me in this and any repercussions. Should I have paid the lot? Should I call the bar and give them DF's details?