Should I have to pay for a crown lengthening if I just had a crown put on that same tooth one year ago?

I had a crown put on my tooth (3rd tooth from back) just one year ago and it had been bothering me for a few weeks so I went to the dentist yesterday. As I was having my cleaning done the technician was asking about the crown and when she touched it the crown basically just popped off. The odor was very foul as if there was either food caught in there or rotting occurring below the crown for who knows how long. My question is considering I paid for a crown only one year ago via the same dentist and now this dentist is suggesting that I have a "crown lengthening" for a hefty fee should I be liable for paying for this or did the dentist make an error with my original crown? Any info would be greatly appreciated!