65536 in 64 bits *actually in 33 bits or larger) is 0 in 32 bits. A 0 error means no error" - most functions and apps return 0 if they work right. Seeing a 65536 status means "developer lost track of what he was doing" most of the time. He looked at a 64 bit number for errors when the function was returning a 32 bit number (which would have been 0, and the program is probably checking for a non-zero error to determine whether to put the error number there or put the word "sent" there.)
I'd guess that the text was delivered.