I don't have much time in this cryptocurrency and so far I have not been aware of any stable currency that has lost its value, I think they were created to keep our money insured by maintaining its parity with the US dollar

Stable coins do loose their value. This mostly caused by the performance of the underlying assets being it a currency, commodity or a cryptocurrency. So, if the underlying assets looses it value then the stable coin is also destined to loose it stability. There was a recent case of this stable coin called TeraLuna which happens to loose it price stability due to the underlying assets that’s Luna facing some fluctuations which lead to it collapse. So stable coins do loose their price value or stability.