One place where you can maybe sneak in a quick check is if your friend is already using their phone for something.
Like constantly glancing at the door of the bar, it makes people think you're looking for something better.
This does not mean you can now leave your phone sitting out on the table or bar.
You should never leave your phone on the table, since not only will you be constantly staring at it, but it ensures that everyone is interrupted not only by the call you are expecting but by your phone's every beep, burp and flicker.
If what they're doing is checking-for-no-reason checking then it's better not to affirm their behavior by engaging in it yourself.
Instead take this lapse in conversation to survey your surroundings like a baby gazelle on the great prairie of life.