Is there a sin incurred by one who feigns prayer after passing wind in a crowded mosque, being unable to leave, and abandoning the remembrance [of Allah]?

You erred by persisting in feigning prayer after your ablution (wudu') was invalidated. What was incumbent upon you, if you were unable to go and renew your ablution, was to sit and abstain from prayer. You must repent and seek forgiveness, and not return to this action.