Why I cannot map key after 'f' or 't' commands?

In normal mode '<esc>' typed after 'f' cannot be mapped. I'd like to remove some highlighting in my plugin but it seems Vim simply exits the 'motion pending' mode ignoring mappings for normal mode. So I have to type <esc> twice, the second of which is mapped. Any way to work around this?

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/vim_use/60f9e579-5480-4364-a531-259cdc9aee22n%40googlegroups.com.