If it was the followers accolade then, when a Hubber is banned, they are removed from your total of followers list and that would mean that an accolade could be removed as you no longer have the commensurate number of followers for that accolade. I presume that there are other accolades where this possible scenario.would have a similar effect.
For helping new users I can only assume that there is a finite 'number of helps' that triggers the accolade. If the total of helps is diminished by a hubber being excommunicated from HubPages then this may have had an effect.
I am sure it is nothing you have done, just the vagaries of using a computer program to calculate when an accolade is reached or not. This program computes the accolades on a daily basis I believe, so tomorrow, after you have helped some more new hubbers, you should see the accolade reinstated.
Don't get too hung up about accolades - they are so important that you can switch them off altogether if you want. Then you won't have to worry about whether or not they are there one minute and gone the next.