no...R2 is Amidala's droid. Anakin was allowed to use it for his starfighter. But you can't tell if Obi-Wan recognized it was the same R2-unit from Anakin. But when Obi-Wan saw Leia's message he looks back at R2 and than he could have known it is the same droid. There are also a lot of protocol droids. If it was the same, he couldn't know, or maybe he did, it still stays a big coincidence. But my guess is, that he recognized them, but what could he say to Luke...that they also belonged to his parents? Would raise a lot of questions. R2 could keep secrets, Threepio not, that is why his memory gets erased.