Specifically, I informed my ex twice, first over 6 weeks ahead of time, that I would be leaving town this weekend for a work convention and would be unable to watch our 2-year-old (I have every weekend visitation from Friday PM - Sunday PM w/ no restrictions). She forgot, is unable to find care for our child while she works on Saturday, and is putting it back on me to find care or she "will just withhold future visits at her desire".

She is the full physical custodian and we share legal custody. The state is Massachusetts. I have never missed a scheduled visit with the exception of one other time where I had to travel out of town for a weekend due to work and similarly informed her well in advance.

Does anyone know if I am indeed responsible for finding care, even though I informed her in advance and have no physical custodial rights?