It also sounds to me like you blew a head gasket. When a head gasket blows; it often does not cause contamination of the oil. Sometimes it causes a compression leak between 2 adjacent cylinders; other times it causes coolant to be sucked into the cylinders; or compression pressure to get into the radiator; and other times it causes coolant and oil to mix. It all demends on where and how much the head warped. If your spark plugs are wet; this means that coolant is getting into the combustion chambers. When this happens; if you ever get the engine to start; it will blow large amounts of white smoke (actually steam from vaporized coolant) out the exhaust.
There are two things which could have caused overheating without the gauge showing it. One would be that the coolant level in the radiator had gone down; but you didn't check the level directly at the radiator, and only checked and refilled the level in the reservoir bottle. When a head gasket leaks; the air pumped into the radiator through the leak will break the siphon action between the radiator and the overflow bottle. If that happens, the coolant level in the radiator will drop, while the level in the overflow bottle does not go down or only drops slightly. If the coolant level in the radiator gets low enough; it will drop below the location of the coolant temperature sensor in the engine; which stops the temperature gauge from showing it when the engine heats up.
The other cause for an engine overheating would be that the electric radiator fan stopped coming on when the temperature got hot. This can be caused by a defective thermal fan switch, or a defective radiator fan relay. Once in a while; it can be caused by a defective fan motor; but that is much less common than the fan switch or the fan relay.
A long shot; but something I still need to mention, is that I have repeatedly seen situations where the use of Sea Foam wipes out a set of spark plugs and stops the engine from running. When this happens; the plugs may become wet.
Since you apparently let the motor run for an hour while the vehicle was not moving; the abnormally light load under this conditon could have created an excessivly lean mixture condition which may have caused the engine to become hotter than normal; but not necessarily to have overheated. If the Sea Foam wiped out the plugs at that time; it would create the illusion that the engine had become damaged enough to not run any longer. Because this is a very real possibility; I would remove the radiator cap when the motor is cold and check the coolant level. If the radiator is full; I would let go of the head gasket theory for now; and buy a flexible ratchet, a 5/8" magnetic spark plug socket, and some wobble extensions; and replace all the spark plugs with either a new set of Champion # 3031 Platinum Power, gapped at .050"; or Bosch # 4307 Platinum + 2, or Bosch # 4479 Platinum + 4 (these particular Bosch plugs do not have an adjustable gap). I would also recommend replacing the fuel filter, checking and replacing the air filter if it doesn't pass light easily, and thoroughly cleaning the idle air control valve and the throttle body. I would also install a set of new Borg Warner spark plug wires, if the wires have not been changed in the last 3 years. Be sure to only remove and replace one wire at a time; in order to prevent installing a wire in the wrong position.