This citation from the VA records the testimony from a veteran who served in Operation Golden Pheasant. He stated that some units, at least, from the 82nd Airborne encountered and engaged Nicaraguan Sandinista soldiers. The applicant had reported seeing dead and wounded members of "death squads" in the course of his assignment. That would explain the Nicaraguan casualties:
The first stressor involves his participation in Operation Golden Pheasant. In pertinent part, he reported that he was assigned as a parachutist infantryman and radio operators for 1st/504th, 82nd Airborne, which was mobilized on short notice and deployed to Honduras in March 1988 for Operation Golden Pheasant, near the Nicaraguan border, where he testified and stated his unit encountered combat conditions. Specifically, he reported that he and his team conducted patrols into areas near the border, that he and his team encountered Nicaraguan Sandinista soldiers and were fired upon and that they fired back, killing a member of a death squad, and that he saw dead and wounded in the course of this assignment. He also stated and testified that a helicopter crashed, injuring the
Battalion Commander and others on board. The Veteran reported he was to have been a passenger on the aircraft as the Battalion Commander's radio operator, but it took off without him and he was very stressed over this. The Veteran described in statements and sworn testimony that the deployment overall was a stressful experience due to the unknown circumstances the soldiers were facing, the proximity of the operation to the Nicaraguan border, the potential for combat, and the uncertainty of how long they might be deployed.
Although the Wikipedia article does not actually mention American casualties (it simply states "unknown"), the citation states that the Battalion Commander and others were injured in a helicopter crash, so we know the US did incur some casualties in the operation.