Does a 1tb flash drive exist?

Yes, but they are slightly larger (for now) than the "thumb drive" versions.

As of 2011, the price for large-scale flash drives has continued to come down. Some 256Gb drives fell to less than $700 USD, and modifications can be made to existing drives to allow 1 terabyte of data storage. The price for an actual 1 Tb drive (solid-state drive) was still in the $3000 USD range in early 2011.