Mensinger has long been involved with and is a champion of Pop Warner football.
"He is saddened someone would try to use this as intimidation," said Lobdell, noting that the councilman will not file a police report.
Mensinger could not be reached for comment.
The sign belonged to Repair Costa Mesa, a group seeking to block city layoffs for which Mensinger voted, but backers of that campaign denied any responsibility for what happened at the councilman's home. They believe the sign was taken by someone else and placed in Mensinger's Mesa Verde-area yard.
The acrylic paint used at the school and on Mensinger's truck were similar, Lobdell said.
Damages to the truck were not noted in value, and Mensinger can probably remove the paint himself, Lobdell said.
Jennifer Muir, a spokeswoman for the Orange County Employees Assn., responded to Mensinger's Facebook post by denying that the OCEA had anything to do with the vandalism of Mensinger's property.
"These accusations are ludicrous," Muir wrote in an e-mail. "We would never do such a thing, and we would never condone it. This just demonstrates the level of vitriol this council member has toward employees, unions and members of the community who disagree with him — that without any evidence whatsoever, he'd immediately blame people who disagree with the council's unwise outsourcing scheme for committing this horrible act."
The association sent the councilman an e-mail Monday afternoon asking Mensinger to remove his Facebook post, which initially listed first names. The post was later updated on Monday with the names removed.
Greg Ridge, who believes that Mensinger was alluding to him in an early version of the post that used the name "Greg," said Mensinger's mention of him by name was "indefensible" and "incomprehensible."
"To say I'm a little appalled is an understatement," said Ridge, a resident supportive of the city employees in their fight against the layoffs.
This was not the first alleged act of vandalism against a sitting City Council official. In April, a brick was thrown through a window of the Costa Mesa bar owned by Mayor Gary Monahan.