On a side note, you should have taken the advice of earlier posters and NOT gone to the bank. You are lucky they did not damage the bill during inspection. I am not familiar with solvent smears - normal smeared ink is usually streaks, not splotches. In any case, the detail of the design should still be sharp with added "smear" extra ink) - the detail would not be wiped away (that would suggest something occurred after printing. Also, it is incorrect to say that the reverse printing is not "raised". It is not raised as much as the bld parts of the front details, but it is all printed by means of engraved printing (except the seals and serail numbers) so all the ink is raised to some degree.
Solvent smears are a whole different beast. It all depends on how the solvent is introduced to the paper/ink. It could have been splashed/spilled/leaked, the wiper mechanism might allowing solvent to pass through, it could be getting flung onto the paper of incoming sheets, etc.... Like I said, I would treat it as legit until several independent people have looked at it. With solvent smears, you really can't authenticate that via a scan, but at this point, OP has plenty of circumstantial evidence to indicate that it is a legit error note. Time to put it in a mylar holder (if OP hasn't done so yet).
Thanks for the info. On closer inspection, I do see good detail under the smear, so that reassures me that it could be real. My point was (not sure how to explain in technically), that if the ink is wiped off (dissolved) with solvent then it seems to me it was probably done outside of the BEP. If the printing is blurred/fuzzy or has bled, then that might support the idea that it is genuine.