Only number 2 is correct. In Spanish, you can omit pronouns such as 'it' or 'he', because it is clear from the verb form what the subject is. You can't do this in English - you have to say 'when it was robbed', so that we know that 'it' refers back to the jewellery store.
By the way, I presume you meant your title to say 'Doubt'. 'Doubt' is an English word, but speakers of Hispanic languages consistently use 'doubt' incorrectly in the language-learning context. If you have a 'doubt', this means you are seriously apprehensive about the value or reliability of something. This post is not a doubt - it's just 'a question about grammar'.