Based on the way the search API works I don't think this is feasible. "dropb" is not a token that the system recognizes as being part of "dropbox" so I think dropb essentially returns no results. It would be nice if they had some sort of autocomplete functionality. That is how Google Instant works- it makes an educated guess at what your query will be and uses that rather than using the partial query. It's pretty effective much of the time.

Seems like ThriftDB is still in a pretty early stage of development so I doubt that they support this. But autocomplete is a solved problem so I'd be surprised if it doesn't make it in at some point.