However, you would still need to use some of the tokenisation steps that he talks about such as finding word boundaries and stemming.
The performance of your problem would be bounded by the size of your unseen text.
Something like the The Knuth-Morris-Pratt string-search algorithm would be useful.
it's a bit tougher than regular string matching because of homoglyph attacks (i.e., people trying to subvert the matching by writing f_ck or f0ck or fȗck or whatever) but I can probably do a pretty straightforward tokenization at ingest time to clean that up.