Hayhāta is not an ordinary conjugated perfect verb. It is an ism fiʿl māḍī carrying the sense “has become distant,” followed here by the nominative al-ṣilāʾu, the warmth sought.
Tanawwartu is a regular first-person perfect verb of form V (tafaʿʿala), with the verbal noun tanawwur. The contrast clarifies the difference between a conjugated verb and a fixed verbal noun-form functioning as a verb.