In CA, a contractor had a home improvement contract that excluded plumbing fixtures and nothing more. The homeowner understood plumbing fixtures to be sinks, toilets, tubs and faucets, which is in conformity with the Uniform Plumbing Code and the CA Plumbing Code definition. As part of the bathroom remodel floor plan, shower glass was to be installed. The homeowner understood the shower glass to be included in the negotiated contract price, though it was not an expressly included item. During construction, the contractor directed the homeowner to go to a specific glass store to pick out the shower glass and handles. The shower glass company then faxed a schematic and work description to the homeowner that did not show any pricing and required the contractors signature, not the homeowners signature. The contractor signed it and it was returned to the glass company. Subsequently, the glass was installed. Later, the contractor presented the homeowner with a single item "change order" for $3,000. The homeowner refused to pay it based upon the shower glass not being an excluded item, not agreeing to the price / change order in advance, being directed to the glass supplier with no knowledge they were expected to pay an additional charge for the glass. Based upon this and other disputes, the homeowner and contractor are going to Arbitration. Is the contractor entitled to reimbursement under the theory of "unjust enrichment?"