H1B denial previous employer approved petition revoked

Hi All,

I came to US in Jun 2017 for employer A with I94 till Aug 2018. Joined employer B in Sep and that petition is still waiting decision. A has revoked the petition.

If the petition is denied, can I stay back and get another petition filed or do I have to leave US?

If I have to leave, then which date would I start accruing illegal stay?