The reasons for regurgitation are many. The most common is inappropriate temps (yours seem fine, but it doesn't hurt to double check them)and stress and/or movement/handling post prandial. I'm sure this isn't news to you.
Less common reasons for regurgitation are toxicity, nervous disorders, intestinal obstructions (tumours?), viral infections, parasitic infections... the list goes on into the more obscure.
In the mean time I wouldn't panic. You've got a fair size boa there so I would imagine a month off of food would be fine right? After this month, feed a smaller rabbit than usual and see what happens. Always make sure your husbandry is top notch and water is always available.
Because you have a well adjusted captive boa of adult size, that is not new to your care, if another regurgitation happens I would recommend a vet visit to rule out some of the less common disorders. If your boa shows any other symptoms while you are waiting a month (lethargic, further vomiting, diarrhea, weight loss ect)then a vet visit needs to happen sooner.