OMG OF COURSE!!
We've seen the pics of Robberz and the curious blonde, and even though they're super grainy, it's gotta be Sienna. We're 99.9% sure.
Why?? Because as we discussed earlier in the week, the two were definitely seen together at the Electric Room last weekend, which is the same place Rob was photographed with this supposed mystery woman.
And as we're sure all of you diehard R-Patz fans know, Sienna is Tom Sturridge's baby mama!! So no, we don't think he's cheating on Kristen Stewart with his best friend's gal. He knows better than that!!
[Image via Ivan Nikolov/WENN.]