Severance is the trigger
A foreclosure that carves one parcel out of a larger tract is a severance event — and severance is exactly what the necessity and implied-easement doctrines turn on. If the split leaves a parcel without legal access to a public road, an easement by necessity may be implied across the parcel it was severed from.
The classic elements are unity of title (the parcels were once commonly owned), severance (the tract was divided), and necessity arising at the time of severance. States differ on whether they require strict necessity (truly landlocked) or reasonable necessity.
Statute-of-limitations interaction
Necessity easements are generally implied at the moment of severance, but the practical timing of any quiet-title or declaratory-judgment action — and any competing prescriptive claim — is governed by your state's limitations periods. Confirm the deadlines for your facts with a licensed attorney; the dispute-pathway map can offer a calendar reminder for time-sensitive steps.
Statutory routes
Some states layer a statutory remedy on top of the common-law doctrine — Florida's statutory way of necessity (Fla. Stat. §704.01(2)), North Carolina's cartway proceeding (§136-69), Pennsylvania's and Michigan's private-road acts, and Georgia's private-way condemnation (§44-9-40). Your state page lists which route applies.