I know this doesn't quite tally with the Criminal Register (slightly different date of conviction and age), but is this your Thomas?
"CENTRAL CRIMINAL COURT - SATURDAY ...
Thomas Hill and William Smith, both 16, were found guilty of stealing pickles and other articles the property of James Brook. Smith was sentenced to be imprisoned nine months, and Hill, who had previously been convicted, to seven years' transportation."
Monday, Feb. 10, 1845
Publication: The Standard