The evidence from the OED doesn't support your theory that "imbed" is just a spelling mistake that caught on. The spellings embed and imbed have coexisted since the word was first used in the late 18th century. The first recorded use in the OED is "imbed":
1778 WHITEHURST Inquiry Earth xii. 90 Marine exuviæ found imbedded near the tops of mountains.
"Embed" doesn't appear until 16 years later:
1794R. J. SULIVANView Nat. I. viii. 62 Calcareous substances are in general found where flints are embedded.
That said, it's always "embed" for me, on the rare occasions when I actually use this word...
Please >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Count yourself lucky as to not feel the wrath of my nerg.