The anchor pin is kinda tricky to install with the trans on the bench so you're not gonna get it back in without removing the pan and probably the valve body.

I can't picture any scenario where the pin would be ejected with enough force to break the tab; more likely the tab was already missing (fairly common). Some folks break the tab off to replace the O ring on the pin.

I wouldn't run it with the band and anchor links flopping around inside.