Well $findfile is an identifier which returns a result. In your case, you specified N = 0, which will return the total amount of results matching your file criteria.
Since you put $findfile as first part of a string, $findfile evalutes to a number, in your case 98, and then tries to execute the 98 as a command, which is why you get the error, since you don't have a command named /98.
The fix is to use something like:
!.echo -q $findfile(..)
or
var %dummy = $findfile(..)
etc.
Greets
