This seller has broken a rule by delivering falsely.
They should have used Fiverr’s resolution center to request additional time. Not doing so is suspicious.
If you believe the seller is genuine, I suggest you immediately request a modification so the order does not complete. In that way the seller can then deliver when they are ready.
If however, you have no reason to believe this, have not seen any sign of work being done or are doubtful in any way I would suggest that you also report this behavior to customer support. It has happened on numerous occasions that buyers have been misled by sellers in this way with the aim of the order being complete without work being done.
If the seller has just broken the rule this once, then it is likely they will get a warning only but if they have done this repeatedly (which Support can check) they may have their account removed - which makes Fiverr a better place.