For starters, I've had Arabesques for over three years and have never had an issue with regurging. The only thing I've noticed with any of mine is, both the 06 Albino Arabesque male & 06 Hypo Arabesque het Albino male have refused meals from time to time. No big deal at all!
I actually think the Arabesques make excellent breeders and pets. I've had great success with both keeping and producing them.
Like some of your other replies suggest, I'd have a necropsy done. That would give you a definite answer and piece of mind! I wouldn't wait though, animals to be submitted for a necropsy should be done fairly quick. I'd put the animal in a zip lock baggy, then refrigerate it, then find a qualified vet to have a necropsy done.
Another thought, do you feed your animals on top of that substrate pictured in your post? That stuff would be questionable to me... I stick with plain old news paper, never had an issue! Other than the animals, sometimes get newspaper ink smudged all over their heads! I've been told by my Vet,that's harmless!
Good luck and let us know what the cause of death was!
Sorry about your loss,
Chaz