Folks who were dining at Catch at the same time as Britney, Wemby and Pauly tell TMZ … after the slapping incident, Britney went to dinner inside the fancy restaurant and her party was seated ... at the same booth where they had seated Pauly.

Turns out Pauly had just gotten seated, he got up to use the restroom, and when he came back, Britney and her group were at his table, where he had left his phone, glasses and fanny pack.

Britney's security, we're told, initially stopped Pauly from getting back to the table ... but they eventually let him through.

We're told Paul greeted Britney and they both kind of laughed off the seating situation, and her manager, Cade Hudson, handed over Pauly's things.

Ultimately, we're told Pauly got seated at a different table ... it's unclear if this was just a mix-up or if Catch deliberately bumped him for BS. ET first reported on Pauly's table mishap.

As we first reported ... video shows Britney approaching Victor on their way into Catch and getting slapped by his security, and eyewitnesses say Britney was in shock and angry during dinner.

Cops investigated the slapping incident and decided against pursuing criminal charges against Wemby's security.