The Colombian internationalist was shown a second yellow card and subsequent red for an offensive gesture aimed at the home supporters, but pictures showed the plastic cup being hurled towards the Light Blues player and his team-mates as they celebrated the goal.
Neither Morelos nor his team-mates appeared to be struck by the missile, but there could well be repercussions for the Fir Park side.
It is not the first time Rangers players have been targeted during a match at Motherwell.
Captain James Tavernier had a lighter and a pie thrown at him during a match in April, with Motherwell identifying and banning the fan responsibles within two days of the incident.
'Well chief executive Alan Burrows said of the incident: “We were able to use our CCTV cameras and, because the match was shown live on television, we had the luxury of studying the footage from Sky’s 24 cameras.
“By using our own CCTV, the footage from Sky Sports and still photography – which proved to be very helpful – we have managed to identify both culprits."