In the question asked, since the underlined word is undetermined. If the underline word is “were staying” only this would probably mean only a simple predicate. Notice that the phrase structure is only composed of a linking verb and the word verb or rather gerund “staying”. Contrarily, if the underlined word is “were staying at a cozy little cabin in the mountains”, this would indicate a complete predicate. Which entails the linking verb the verb and the situation which describes the sentence.