Can anybody tell me what this (possibly sexual) gesture means?

OK, so this has had me wondering for a good number of years now and I've looked it up and couldn't find anything so I figured I'd ask here.

When I was 13 I was in a shop that sold band merch in London when the owner of the shop stops me from leaving and tells me to look upstairs, which I declined. He then starts telling me to wait and take a look, and points to the stairs, upon which was now a young woman. He then says "you can [gesture] her". At that point I was pretty freaked out and just left the shop. There was obviously something fishy there, and I was fairly certain the gesture was sexual. But I never came across it again.

So here's what he did: he got both his index fingers and put them on both corners of his mouth. Then he kind of stretched his lips towards the sides of his face with his fingers. Then I think he stuck his tongue out a bit. I can kind of imagine what it might mean but I want to be sure. He was definitely a creep and I felt very uncomfortable.

 

Thanks for the comments, guys. It was pretty terrifying for me and I'm glad I ran out as quickly as I did. I always think I had such a close escape - what if I'd said yes to taking a look upstairs?

Just to clarify, the gesture isn't the one in thr smiley people have been posting. Rather than using the two fingers of one hand and poking his tongue through, he had both index fingers of both hands placed just at the corners of his mouth, pressing down and stretching his lips outwards. He only stuck his tongue out a little bit as well, not like flicking it around, just the tip.