In most American accents, the two words are homophones, so misspelling one as the other in writing is quite common.
[1] http://www.dictionary.com/e/different-from-or-different-than...
[2] https://en.oxforddictionaries.com/usage/different-from-than-...
At least not in the same way "pen" and "pin" are homophones in parts of the country. Nor how they're / their / there is for everyone.
(I know I have a major tendency to write "then" when "than" is meant).