Laboratory furnaces that are used to determine how much of a sample will combust and how much is left behind as ash operate at 550 C (a bit over 1000 F), so we know that is too hot. This is also the clean cycle temperature of many self-cleaning ovens. If you indeed burned off the seasoning, the temperature of the skillet must have been really hot.
I have cooked steaks using the sear-then-into-the-oven method a number of times. The procedure I use includes coating the steak with oil, then searing it. It is important to pick an oil with a fairly high smoke point, such as refined peanut oil (450 F) or extra-light olive oil (450 F). You can heat your skillet to 500 F with these oils and the smoke won't be too bad. The oven temperature I use is on the order of 450 F.
I suspect that if you have a well-developed seasoning, smoke generated from it will be minimal at 450 - 500 F. Smoke means that volatile compounds are being released from the seasoning, but the seasoning isn't actually burning off.
My suggestion is try using a high smoke point oil, preheat you skillet to 450 F in the oven, and keep the burner heat under control so you maintain a skillet temperature in the 450 - 500 F range. Another searing suggestion is to use a skillet (or two) as a weight to keep your steak pressed down firmly while it is searing.
