Minty45,
I wonder whether the gas disappeared because you "forgot about it"... and reappeared causing you to remember? or whether you were able to forgot it as soon as it disappeared (for whatever unknown reason) and when it returned you were reminded?
If you are right and getting your mind focused on something else - something calming - will be helpful, then yes, I do know a breathing technique that might help you. If it proves -not- to be helpful tho, don't give up right away. Instead, try another breathing/relaxation technique.
Remember that relaxation techniques don't "fix" anything, they are a coping mechanism. They can re-direct focus, promote relaxation, lower heart rate, improve mood and buy time to plan proactive solutions, but they aren't a cure and they do require practice to work well.
This technique I suggest is called box breathing. According to the doctor who taught it to me, it is sometimes used by people in high stress jobs like first responders, soldiers under fire, and war correspondents. To practice it, find a quiet place and get comfortable, as you will need to use your imagination together with your breathing for at least 20 minutes.
The box breathing exercise: Imagine stepping into an elevator and rising up one side of a block-shaped box (or a building). You are on the outside of the box, not the inside.
Inhale slowly through your nose as you rise, for the 4 full seconds it takes for you to go from ground level to the top of the box/building.
At the top, hold your breath without adding pressure (don't puff your cheeks out, or make faces) for 4 seconds while you imagine leaving the elevator to walk across the top of the box/building.
Step into another elevator on the far side of the building, and exhale slowly through your mouth while the elevator decends: 4 seconds.
At the bottom you cross under the building in a tunnel (or perhaps your building is mysteriously hovering above ground level? Mine does!) while holding your breath: 4 seconds. Then step into the elevator again and repeat. Continue at least 20 minutes.
In a nutshell: inhale through the nose 4 seconds, hold 4 seconds, exhale through the mouth 4 seconds, hold 4 seconds, repeat.
Synchronize your breathing with your imaginary trek up, across, down and back across the box or building. This couples your imagination with the physical activity and measured breathing, producing full relaxation, health and focus.
Once you get the hang of it, it can be fun to wear a "pulse-oximeter" and watch your heart rate fall and O2 level improve while a sense of calm assurance spreads over you.
If you feel breathless, relax by focusing on the box (imagination/mental exercise) and allowing the process to develop its own 4-second rhythm.
If you feel dizzy, relax your breathing. Let it happen, rather than making it happen. Just keep it on that 4 second rhythm... or as close to it as is comfortable for you. You should wind up feeling relaxed and empowered.