Is the Nano powered via a USB cable ? If the 3.3 volts is derived from the USB/UART chip (in clones usually a CH340) then 3.3 volts is available only when a power connection is made over the USB port.
Anyway, it is probably best to get your set up working in the more conventional mode, that is the receiver permanently waiting for a transmission and the transmitter sending something regularly, say every five seconds. Once that works, then attempt to get it to work in the "one-shot" mode you have described.