No luck on my part either.
I did think of a fourth possibility. I don't know that MA law provides for a 'pocket veto' like the federal system does. If a bill is passed at the end of a congressional session, the president's refusal to sign the bill effectively vetoes it without him actually doing so. As I say, though, I don't know if MA law has this provision.
I am in the same boat as you. Maybe someone in MA will chime in sometime to let us know exactly what happened here.
The only other thing I have been able to locate was some law maker named Donato evidently was involved with this bill. But, finding info on why the amendment never saw the light of day?? No luck so far.