My mother and I have suffered with trapped gas our lives long. It can be extremely painful and i sympathise with anyone who gets this.
The way we handle it is thus:
Sip warm water, slowly, untill gas starts to move. If this does not work:
about 2 inches of warm water, very warm but not hot, so that you can drink it. One teaspoon of bicarbinate of soda. Stir it in and down in one go. Very salty so be warned. If you dpont start to burp and pass gas within an hour, same again. My mum, who does not have ibs, just nervous tummy, finds that if she curls in a ball and rocks after taking the bicarb it helps things along. This does not help me, so its you call.
Warning, i was told bicarb was not good for people with high BP, but my mum is fine with it, and on 2 occasions it has given me an awful D attack, but then no gas after. This is just something we do, passed on down the generations of bad tummy's on my mothers side!