Yea, as the previous Al said, we need to know the internal temps of the butt. As long as it didn't take over 4 hours to get to an internal temp of 140 you are fine. BUT you didn't use a thermo so we are just guessing. You are Rolling the dice, 175 chamber temp is just to low to even guess what the internal temp on the butt got to. Sorry.
You learned two important lessons, use a thermo to monitor the internal temp of the meat, you could have gone to bed with the cooking chamber at 170 if you had gotten to the magic 140 internal before leaving it.
Good Luck,
Sorry I can't tell you yes or no on this one.
Don't forget to go to the new members section and introduce yourself, we will be able to help out a lot more once we have an idea of what equipment your are using and your experience level.
Al