Nancy:
We also are seeing more and more auctions... and in many sub-markets they are pretty much defining the market... in my area moving water properties on streams and rivers are hot properties, and I do mean waaaay beyond reason!
One of the criteria I use to determine if any auction sale was 'adequately exposed' and more closely approaches a Market Sale and clearly defined as an 'arm's length transaction' is the number of potential buyers - as opposed to lookie-loo's who are showing up for amusement value, and the extent of advertizing...
No Reserve Auctions can be just plain weird, sometimes they go for way more than prior listing of the same property, sometimes way under

so what was the market on sale day as direct competition, and who showed up become criteria for serious contemplation before the sale can be considered 'comparable'!
I agree with Pam, it depends.
In your case I think I'd ask about other sales in the sub-market, how many times were they shown before they sold? If you got more 'serios' potential buyers at the auction..... than looked at the other sales in the submarket methinks you have 'exposure'.
I wouldn't rely on that sale very heavily since it was 'odd' for your market and sold well below one of the prior offers, adn significantly under the prior list. But I'd sure throw it into the grid and 'splain!