thought
The Italian word 'pensato' is the past participle of the verb 'pensare', which means 'to think'. It is used to express an idea or concept that has been considered or reflected upon. In English, we might say 'I have thought about it' or 'I thought about it yesterday', which in Italian would be 'L'ho pensato' or 'L'ho pensato ieri'.
I thought of calling you
This sentence uses 'pensato' in past tense. Here, 'ho' is the first person singular of 'avere' used in the compound past tense, 'pensato' is the past participle of 'pensare' which means 'to think', and 'di chiamarti' expresses the intention to call.
I had never thought about this
In this sentence, 'non avevo mai pensato a questo' 'pensato' is used in the compound perfect tense. 'Non avevo mai' translates to 'I had never', 'pensato' is the past participle, and 'a questo' refers to 'about this'.
You thought you had lost it
Here 'pensato' is used within a compound sentence. 'Tu hai pensato' uses the second person singular of 'avere', the past participle of 'pensare', and 'di averlo perso' translates to 'you had lost it'.