Wet phones are typically a bit challenging, for sure. If you're still not able to get the device to read your SIM card, you may need to look into a replacement device. The warranty is voided with the water damage, but since it sounds like you have Premium Handset Protection, you could file a claim with Asurion to have them send you a new device. You may also be eligible to upgrade your device, and to find out more about that, you'll want to log in to www.t-mobile.com with your mobile number and password to see your options there.
It is possible that the phone will come back to life - I've seen them go through the washer and still survive - but the drying process can take a few days. You're doing all the right things. You may also want to try a different SIM card in the device, in case the liquid affected your old SIM card.
You may also want to look into some options for cases, just in case the endeavor to keep the device out of 2 year old hands is not successful. They're small, but they're cunning.