take it from a fellow vix trader, you did nothing wrong really in theroy, just the execution. before you ever buy any EFT you want to pull up charts and see if it follow the other stocks or ETF's.
One big waringn sign was that the vix trades in a range of 15-22 on average, so so last week if vix was at 17.50 and UVXY was at 9.50 then it drops to 16 and uvxy drops to say 8.50 then when vix goes back up to 17.50 uvxy should go back up to 9.50
if you look at the history you would have seen that the vxx, tvix and uvxy do not trade as the vix does and that is the issue. so it would be wise to stay away or trade it with stops.
there is also anouther way to trade volitiy, using the dollar, gold or maybe oil. 95% of the time if the vix goes up then there are issues in the market that will effect the dollar and gold.
or dont trade teh vix ETF's insead trade the dow ETF's
contango is what is destroying the value of these funds, and today is a perfect example VIX is up and all the ETF vix's are down.
dont forget to really play the vix you have only one choice and thats OPTIONS on the vix but they are expensive.