No, F1 Hybrid is not an accepted species name, Joanne. ITIS and GRIN both state that only Petunia hybrida (or Petunia hybr.) is accepted, not Petunia x hybrida, F1 Hybrid, or any other variation of the name. If "F1 Hybrid" is meaningful information, it probably should be included in a comment or perhaps in the common name field. Is it conceivable that someone would include it as part of the name during a search?