Losing is very hard to rub off, especially when you lose a lot of money in one night, I can easily rub it off now but when I was starting out it was hard for me.
I have a friend who always shows signs of obvious loss in gambling, and he always shows body signs like he doesn't want to talk to anyone and always looks far, always trips himself because his mind is wandering.
Now, do you have a body sign that people around you can tell if you lose money in gambling, I'm sure all of us have one, be honest with yourself

your friend signs is actually a normal signs of a Loser, specially if the money he losses is important to Him , maybe if he losses his allowance or even the funds for the food? it is normal to show that attitude because they are looking for another way to earn money to use to gamble again and to recover their losses.
I have no other sign when lose but like your friend? i remain silent and thinks deeper for how to win back my money.