Several things strike me as wrong about this.
First, it is incredibly presumptuous to leave a tract that basically says you know the spiritual condition of a person you interacted with for mere minutes. Evidently, being saved gives one super powers to determine this. Or not.
Second, it is a poor witness. Reducing Christianity to a pie-in-the-sky vision of eternal life leaves no way to discuss the love God has for this person right now. This person needs to put food on the table and has various needs that are now not fulfilled. Sure, as the tract says, "Some things are better than money." But few waitresses I have worked with are doing that job because the money is so damn good.
Third, it is injustice. For whatever reason, our society perpetuates the myth that tipping is something people give as an extra... a bonus for good or bad service. What we must realize of course is that the servers' wages are almost exclusively tips. The minimum wage for such workers is abysmally low, and hasn't kept up with federal minimum wage law very much at all. Don't muzzle the ox as it treads grain, and tip your waitstaff twenty percent at least. Every worker deserves to be paid.
The tipping point for me in this discussion (yes, pun most definitely intended) is the Lord's Prayer. I realize few Lutherans would ever pull such a crappy move, because we don't generally hand out tracts (The ability to share one's faith might also be called into question... but tract leaving is definitely not about sharing one's faith). But there is also a place to turn to consider our restaurant manners in the light of our faith, the Lord's Prayer. More specifically, "Give us this day our daily bread."
When we consider all that must happen for us to receive that meal, we cannot consider the waitress a dispensable link in the chain. To faithfully pray as our savior taught us, we are to give thanks for everything required to bring us our daily bread. And just as we would not expect the supermarket to take a "Get Saved" tract in exchange for our groceries, neither should we leave it for a person seeking to live off of that job. Being thankful is not just a state of mind, but an active response. If you feel it necessary to leave a tract, make sure you also tip well. If you cannot afford to tip, you cannot afford to eat out.