Q: Leaking power steering oil

Hi there, I got an oil change recently where when my car usually takes synthetic oil the mechanic accidently used non-synthetic. Now this may not be related at all but 2 days later my car starts to make a funny noise. I take it to the mechanic and he says my power steering is leaking as the fluid was low. We topped it up and I proceeded to check on it. A few hours later, the noise returns and i check the oil and its below minimum. However the I see no leaks under the car. I continue driving to the nearest gas station to buy power steering oil which was 8mins away and when i get there the fluid is totally empty! However dispite the empty oil the steering is fine and still working great but the noise is back. Questions: Where is the oil going? What could of caused this so abruptly? Is there a correlation btw wrong engine oil being used for oil change? Do you think its the power steering pump or hoses? or something else? How dangerous is it to be driving with no oil? Paulina

My car has 93 miles.
My car has an automatic transmission.