Can you be fired for something that happened 3 years ago?

I modify mortgages for a bank. A customer issued a formal complaint about the way I handled her file. She said she was offended by my suggestion that she reduce expensesand that she could have been given better terms. My manager backed my decision and mannerisms 100%. We are encouraged to recommend customers lower expenditures and all our calls are taped so my politeness about the issue is on record. She also filed a complaint with the occ. The customer then dropped the complaint… Out of the blue… With no further action. This was in 2011. Today I get an email saying the issue has been forwarded to security and HR. I told my manager and she was absolutely clueless as to why this was happening… And it wasn't an act. This is very strange… Any input will be appreciated.

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