Issues with a bootloader

[Art]

If the boot loader can write your program over serial the pic must support program memory read/write.
So you should be able to check if the loader exists with your own pic program.
If you think you're overwriting it with your program you'd only need to check the first word is correct.

pword var word
index var word

index = $7F40
LCDOUT ... clear screen and home command
READCODE index,pword
IF pword = $700E THEN
LCDOUT “  Loader exists   "
ELSE
LCDOUT “Loader Overwrite"
ENDIF