Forced 6th Day question


As most who've spoken with me know, I'm a Tues-Sat 22.4. We've been forced in on Mondays for quite a while, so in effect I'm a Mon-Sat 22.4.

Today we had a super light dispatch-- only about 30 routes went out of my center. The 22.4's almost all were scheduled off. All routes were covered, all RPCDs were present in-building and ready to work. Right after PCM, one of these drivers came pissing and moaning to dispatch about not feeling well.

After some back and forth bickering, I get called up and put on-route at the last second while the RPCD gets to go home despite bluffing that he was here and ready to work.

I'm cool with the all-day overtime, but I want more. This is the first Monday I would've had off in ages, and I wanted it. That said, I'm trying to figure out how to write up a grievance based on sending home scheduled workers and forcing unscheduled workers to cover on their day off. Gonna talk with a shop steward in the AM but in the meantime I kind of wanted to get everything lined up, but I might be SoL because I'm having trouble finding any contractual language about this for 22.4s. Any help would be appreciated, even if it's just to let me know it's a losing battle and not worth filing.
Or….. stand up directly to the RPCD that is the issue.