If you offer a stop loss would you not simply put the coins for sale at the stop loss? How can they end up not being sold then?
Example:
1. imagine you have 10k BTC
2. set stop loss @ $130
=> there is not buyer who can buy your coins
The only way you could do it would be to have the script / engine monitor the bid depth and dump accordingly and in advance as the price falls.
If someone else dumps a large amount of Bitcoin - something like 5-10K moving the price straight past your stop loss trigger point then you would be out of luck and could end up missing your sell point by a large amount due to the low liquidity and huge swings in this market.