By your description with the coolant gauge and radiator appearing not to be overheated, you may have blown a head gasket. You can request for a coolant pressure test to have visual on your system breech.
Here is a great link to further investigate about blown head gaskets
This sounds pretty serious. Most likely the cooling system has a leak and due to the leak, the coolant level got very low which caused the engine to overheat. It sounds as if it overheated to the point that it seized. Your temperature gauge will not reading correctly unless the sending unit is in contact with coolant. It is possible for the temp to appear normal when in fact the engine is overheating to the point of damage. You need to have the engine checked over completely. You can expect at a minimum to have to fix the leak, replace the thermostat and possibly the coolant temp sending unit and the engine coolant temp sensor if it has one. Those three parts can be damaged by overheating the engine.
〉 Answered on Dec 17th, 2009 by Judy Curry, Co-Founder and Vice President of Marketing at Currys Auto Service
The temperature gauge may have malfunctioned, or the coolant level was so low that it did not activate the temperature sender which is usually located at the top of the engine. Since smoke was visible, possibly indicating a severely overheated condition, and the engine does not turn over, the engine may have overheated to the point where it seized. Should inspection reveal little or no coolant in the radiator, this is likely what happened. Sorry about this- but I hope this helps- Super Girls Auto.
〉 Answered on Dec 15th, 2009 by Laurie Sarno, Co-Owner at Super Girls Auto
Smoke coming from the engine compartment does not always indicate the vehicle has overheated. There are many things that can cause smoke in an engine compartment, such as any moving part rubbing on something that it shouldn*t be, an electrical problem, or fluid dripping on hot parts. It*s probably best to have your vehicle looked at by a qualified technician to first determine exactly what caused the smoke.
〉 Answered on Dec 16th, 2009 by Suzanne Grego, Technician at City of Philadelphia Fleet Management