No sign of the mother's death yet, post-1841 census. Could she be with daughter Sarah somewhere else?
Not sure if you're using Ancestry or Family Search, but this might be son John Tosler in 1851.
His occupation is "cooper". Note that Ancestry have transcribed the surname as "Fosler".
Name: John Fosler
Estimated Birth Year: abt 1811
Relation: Head
Spouse's Name: Nancy Fosler
Where born: Hull, Yorkshire, England
Civil Parish: Kingston upon Hull St Mary
Sub-registration District: St Mary
ED, institution, or vessel: 2
Household Schedule Number: 90
Piece: 2362
Folio: 388
Page Number: 20