David Tennant's sonic screwdriver had not been given away yet. Supposedly, Matt Smith still has his last sonic screwdriver. Now, he did get three other sonic screwdrivers after John Hurt's one(Eccleston, Tennant,and Smith). Tennant technically got another sonic after he dropped in in "Partners in Crime". But remember, same software, different case.
They mean in the christmas episode, "A Christmas Carol", he gave it to teen Kazran Sardick.
Yes he did give it away, but we can assume that when he built a new one, he used a backup copy of the screwdriver's software stored in the tardis computer system. The 11th Doctor afterall put a charger into the tardis console for it, so why not process software updates through the same system, much like a USB drive.