I realize this question was asked 10 years ago, but thought I should share my insight still:
To answer your question: Yes, gas can trigger the vagus nerve!
There's actually a condition called Gastrocardiac syndrome (also known as Roemheld syndrome) in which gas in the stomach or intestines may put pressure on the vagus nerve (as well as the diaphragm and/or heart). There's a lot of literature on this in German, and in recent years more has been translated into English (including the original works of Dr. Roemheld, whom first described this syndrome).
Treatments are many, and depends upon the underlying reason for the gas.