Ok, I don't actually know if this R4 was seen on Tatoone, because I have yet to see him anywhere at all (DVD almost here....) but he's sorta grimy, so I consider it a strong possibilty. It's either there, the streets of Coruscant, possibly on the streets of Naboo (that one disembarking shot) and that's really it.
UPDATED - Thanks to the DVD I found this R4 Unit, he's actually not in the film, but can be seen "parked" outside Dexter's Diner in one of the documentries.
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