Thanks to the Legal Writing Prof Blog for the following reference to a Wisconsin case:

FN5. Counsel for Espitia cites to an unpublished case assertedly upholding a stipulated damages clause due to the difficulty of ascertaining “the exact amount of income certain vending machines would produce.” The cite provided is “ Buellesbach v. Roob, 2005 AP 160 (Ct.App.Dist.I).” Buellesbach indeed is unpublished but it has nothing to do with liquidated damage clauses or vending machines; it is a misrepresentation case brought by newlyweds against a wedding photographer. Also, “2005 AP 160” is the docket number, which we discovered only after reaching a dead end at 2005 WI App 160, 285 Wis.2d 472, 702 N.W.2d 433. At last we located the unpublished case that addresses the subject matter for which counsel cited Buellesbach: Stansfield Vending, Inc. v. Osseo Truck Travel Plaza, LLC, 2003 WI App 201, 267 Wis.2d 280, 670 N.W.2d 558. Different name, different citation, different district (District IV) but, as promised, unpublished. It is a violation of Wis. Stat. Rule 809.19(1)(e) to provide citations which do not conform to the Uniform System of Citation and of Wis. Stat. Rule 809.23(3) to cite to unpublished opinions. One reason may be that they can be time-consuming to locate. A $100 penalty is imposed against Espitia's counsel. See Hagen v. Gulrud, 151 Wis.2d 1, 8, 442 N.W.2d 570 (Ct.App.1989).

Espitia v. Fouche, 2008 WI App 160, ¶ 14 n.4, 314 Wis.2d 507, 758 N.W.2d 224 (Ct. App. 2008) (unpublished table decision).