It is thought the permanent transfer of the Aston Villa frontman was on the table but the two parties could not agree on personal terms.
Hughton is still keen to sort out a three-month loan agreement for Harewood ahead of Newcastle's next league fixture - a trip to Cardiff .
United have made a strong start to the season and Amoebi's goals have been a crucial factor but he is facing a two-month lay-off with a stress fracture of his right foot.
Hughton told the Newcastle Chronicle: "Shola has been a really important part of things so far this season.
"It is not just his goals, it is his influence off the field. He has scored goals and has played well. He'll be a big miss."
Loaned outFive goals in five games has re-ignited Amoebi's career and standing within the Geordie faithful.
His efforts have played a major part in taking Newcastle top of the Championship table and Hughton hopes Harewood can help his side maintain their momentum.
The Villa striker is out of favour with Martin O'Neill and last season was loaned out to Wolves for two months.
But Hughton does have another option if he fails to land Harewood.
Peter Lovenkrands returned to St James' Park as the transfer window closed. The 29-year-old Dane was released by the club in May but has now signed a three-year deal.