This is why you don't move in without a ring on your finger!

We spotted moving trucks outside Ben Affleck's $20M Pacific Palisades mansion this afternoon, and workers were busy hauling boxes and wardrobe containers out of the home. Clearly his ex Lindsay Shookus is getting all her stuff back and getting out of dodge, in the wake of his new romance with Playboy model Shauna Sexton!

The saddest part? The SNL producer had just moved in at the beginning of July! Talk about a waste of time and effort.

Multiple sources have told us that the cause of their breakup was threefold. Firstly, their long distance relationship and work commitments on separate coasts made things difficult, and the Oscar winner's battles with addiction and sobriety didn't help things. Then there was the fact Jen Garner wasn't Lindsay's biggest fan, and didn't want her anywhere around their three children, making cohabitating nearly impossible.

A source tells X17:
    "Jen is thrilled that Ben and Lindsay are over. She would rather he be with anyone but Lindsay, since she was the mistress that broke up their marriage. Of course, she thinks it's childish and ridiculous that he's going after a Playboy model half his age, but she'll take it. Jen's worst fear was Ben popping the question to Lindsay and having another baby, so she's relieved she doesn't have to worry about that anymore."

That said, Jen G didn't seem too "thrilled" last night when we asked her about her former spouse's hookup with the pinup after her Hollywood Walk of Fame star ceremony. Watch her reaction!