With on input, the text entered is in $1-, which is what you need to check for any comparisons.
on *:input:#help: { if (<truguce* iswm $1-) write -ai truguce.txt $1- - Added $date }
I'm not sure why you have the -ai switch in the write command, as the -a switch appends the text, and the -i switch inserts the text, both (to my understanding) require a line identification of some kind, which is missing in your write statement.
If you're just wanting to write the information to the file when there's a match, you can remove the -ai switch. Noting as how you're using an * in the match, I'm presuming that you're actually wanting a wildcard match, rather than matching the * as a specific character.