Omitting the /s/ is an oversimplification. Classically what happens in accents like that is that /s/ is rendered as [h]. People do this aspiration to varying ex

Omitting the /s/ is an oversimplification. Classically what happens in accents like that is that /s/ is rendered as [h]. People do this aspiration to varying extents, sometimes omitting totally, sometimes not. Presence of a vowel following nearby can make a full formed [s] appear. The "a" in gracias a dios could easily make that into "gracias a dio". By the way I had a coworker who was a native Arabic speaker say "thanks God" a lot. I think "thank God" is a phrasing that throws off a lot of people learning English, from multiple language backgrounds.