navernoe vs. naverno

[Emily Tall]

Could anyone tell me what the difference between the above two words is,
if any? My 4-volume dictionary says they are synonyms and doesn't give
any stylistic difference, while a native speaker friend says it is
always written "navernoe" even though pronounced in conversation as
"naverno." However, I have found it in written speech in literary works
as well. Any enlightening replies are welcome.
Emily Tall mllemily at ubvms.cc.buffalo.edu