I had to leave a Trombone Shorty concert in Centennial Hall in Tucson for this very reason. Even supposedly experienced Sound Engineers relegate the bass to the sub woofers; because that’s where it goes, right?
Just make sure to have a conversation with the Sound Engineer when this happens to you, to hopefully save his next victim the agony. Explain that the bass guitar goes in the Mains, and then bring up the signal in the subs to warm things up. They should know this. But, there is now an entire generation of Sound Engineers which trained in their Honda Civic with 2000W sub woofer, and thinks that’s the way music should sound. I wish that was Sarcasm speaking; but, not the case.