Elements.   Promissory estoppel is an equitable claim that is unavailable when an express contract covers the dispute's subject matter. See Fortune Prod. Co. v. Conoco, Inc., 52 S.W.3d 671, 684 (Tex. 2000).  The elements of a promissory estoppel claim are: (1) a promise, (2)  foreseeability of reliance thereon by the promisor, and (3) substantial  reliance by the promisee to his detriment.   Henry Schein v. Stromboe, 102 S.W.3d 675, 686 (Tex. 2002).  

Statute of Limitations.  Promissory estoppel has a four year statute of limitations.  Ambulatory Infusion Therapy Specialist, Inc. v. N. Am. Adm'rs, Inc., 262 S.W.3d 107, 119 (Tex. App.—Houston [1st Dist.] 2008, no pet.)