Passive-Aggressive Neighbors

The guys who mow our lawn park across the street when they mow. I'm assuming they do this so they can get where they need to mow & edge. Last week I happened to notice they parked in front of the empty lot owned by my across-the-street neighbor. His house is adjacent to the lot. They parked mostly in the street (not on his grass) and used cones to notify drivers they were there. They did not park in front of his house. When they came to mow today, they told us the neighbor called the HOA on them for parking IN FRONT of his EMPTY LOT. Seriously? Why couldn't he come ask us or them to move? I bet we never hear anything from him about it. Such an ass.