I have acid reflux and was given ketorolac?

This med is an NSAID and you may have more than acid reflux, you could have an ulcer or diverticulosis and it made you bleed from an already irritated ulcer or diverticula. If you start running fever, or get much worse, go back to the ER. If you think you are ok until Monday, get to the doctor as soon as you can Monday and get this checked out. The black look is likely old blood, from the start of this episode.

Ketorolac are a nonsteroidal anti-inflammatory drug (NSAID). It may cause an increased risk of serious and sometimes fatal heart and blood vessel problems (eg, heart attack, stroke). The risk may be greater if you already have heart problems or if you take Ketorolac for a long time. Do not use Ketorolac right before or after coronary artery bypass graft (CABG).

Ketorolac may cause an increased risk of serious and sometimes fatal stomach ulcers and bleeding. Elderly patients may be at greater risk. This may occur without warning signs.

Do not use Ketorolac if:

you are allergic to Ketorolac, aspirin, or any other NSAIDs (eg, ibuprofen, celecoxib)
you are taking aspirin or another NSAID (eg, ibuprofen, celecoxib)
you are breast-feeding or are in labor
you have recently had or will be having CABG
you have a stomach ulcer or a history of ulcers or severe stomach problems (eg, bleeding, perforation)
you have severe kidney problems or are at risk of kidney failure (eg, low blood volume, dehydrated)
you have bleeding in the brain (eg, stroke, aneurysm) or bleeding problems (eg, platelet disorder, hemophilia), or you are at risk of bleeding

Read more: https://www.drugs.com/mtm/ketorolac-nasal.html#ixzz0oheU6Itz

I think this is why the guy at walgreens was surprised that you were given this med.