One of the Promos for The Force Awakens shows R2-D2 and C-3PO meeting BB-8 in a desert, probably Jakku.
Where in the movie was this supposed to go?
That scene was invented entirely for that promotional clip, and has nothing at all to do with the plot of the movie.
Note that the clip is not a Star Wars: The Force Awakens commercial, as it has sometimes been incorrectly labelled on YouTube. It's a commercial for a UK mobile service provider, O2 as you can see from the quote and clip below.