Having netted three goals in ten games for the Daggers, Montano was due to return to West Ham after Saturday's crucial clash at the foot of League Two against Northampton Town.
Now though he has been loaned out to Notts County, a second spell at Meadow Lane this season for the Colombia-born 20-year-old.
"At the end of the day he is obviously their (West Ham's) player but it is really disappointing for us," manager John Still told his club's official website.