Hello!

There is some randomness on what you discover in ancient ruins. However, a survey ship and a leader with the 'Explorer' skill will help increase your chances of finding something in ruins. The 'Galactic Relic Collection' wonder will also increase your chances.

With respect to your specific question, a unique technology found in ruins is only discovered once in a game and can only be used by the player who founds it. So, if you find, say, 'Adamantium Armor', no one else should have access to it from searching in ruins. However, there is one galactic event that will allow you to share a unique technology with another empire. That is the only exception.