What is the ruling on owning and using two computers that were purchased at a low price after riots resulted in these devices being stolen from a telecommunications company, bearing in mind that the buyer did not know or suspect their origin at the time of purchase, and is his conscience cleared before God by that?

As long as you bought the two devices unaware that they were stolen, there is no sin upon you. However, the device remaining with you belongs to the company and must be returned to them, even by stratagem. The same applies to the value of the device you sold, because it was lost while in your possession and became your responsibility. This is because liability stems from the nature of the transaction itself and is not waived by mistake. You should claim back the price you paid for the two devices from the person who sold them to you. If it is impossible to return the devices to the company, it suffices for you to donate their value to public welfare projects for Muslims.