The Collaborative International Dictionary of English v.0.48:

Mislay \Mis*lay"\, v. t. [imp. & p. p. Mislaid; p. pr. & vb.
   n. Mislaying.]
   [1913 Webster]
   1. To lay in a wrong place; to ascribe to a wrong source.
      [1913 Webster]

            The fault is generally mislaid upon nature. --Locke.
      [1913 Webster]

   2. To lay in a place not recollected; to misplace; to lose.
      [1913 Webster +PJC]

            The . . . charter, indeed, was unfortunately
            mislaid: and the prayer of their petition was to
            obtain one of like import in its stead. --Hallam.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mislay
    v 1: place (something) where one cannot find it again; "I
         misplaced my eyeglasses" [syn: misplace, mislay,
         lose]

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "mislay":
   be bereaved of, default, drop, forfeit, go astray from, incur loss,
   kiss good-bye, let slip, lose, lose out, mislocate, misplace,
   misput, miss, sacrifice, suffer loss, undergo privation,
   wander from