Ragnick says the club are still hopeful of signing Lookman before the transfer window closes on Friday, having made a bid of £25m plus add-ons for him on Saturday.
Rangnick said: "We'll see. Let's just wait another week. When you turn back the time to the last day of the last transfer market, at 2pm we didn't even think about a loan of Ademola Lookman.
"It seemed impossible to get him. But four hours later we got the deal done. I said then that it wasn't a last-minute deal but a last-second deal."