If you want, the auto engage thing is just a spring problem. You'll find with almost every reel that is supposed to do something when you turn the handle.......whatever it is supposed to do is 9 x's out of 10 done with a spring.
this happens a lot with the old Quantum baitcasters and some reels with flippin' switches. Quantum is general always seems to have problems with the internals of their reels.
With the Daiwa spool tensioner.....I'm sure if you emailed them and asked they would send you one. Most companies don't hesitate on small parts like that, if anything it would cost $5