Hi,
I could only think of water which flew down to the gearbox itself, but I'm not too familiar with the wirings of the automatic transmission. There is no possibility that water came to the ECUs and they became wet? Usually engine sensor problems don't cause all lights to went on but it's definetely a fact that problems with the throttle valve sensor cause the transmission ECU to lock the 3rd gear for safety reasons, so that misleading values derived from the throttle valve sensor don't cause harm to the transmission.
Having the transmission in safety fallback mode with all lights on usually points to problems with sensors of the transmission or even worse mechanical problems (but that seems to be unlikely in your case). But it also tells you that something is seriously wrong at the moment and that you should avoid driving around unnecessarily - in the end some things happened at the same time and you have e.g. too less tranmissions fluid, who knows?
Please readout the errorcodes stored in the ECUs fault memory so that we can border the problem.
Many regards
Bastian
