Looks like you've found the answer, but another trick that often works, at least for devices that are certified for use in the USA, is to search the device for an FCC ID, and google that id. The FCC maintains a lot of information about approved devices, including what frequencies they transmit at, and often modulation protocols, and other nifty info. It's so easy and cheap to get that info, it's always worth a check.
Assuming that strategy doesn't yield any information for you...
Since you've found that it's transmitting on 433, and you've been able to receive it, be aware that most devices in that band use simple on-off keying. If you can receive anything at all, then hook the output of the receiver into an oscilloscope and see what you can see. Or if you can take the device apart, you may find a logic level input to the radio transmitter, and if so, you can use a scope to figure out the timing of its on/off pulses.