As I have written in a previous post, when error are discovered in financial statements, these errors should be corrected at the next available opportunity. This can mean re-stating published accounts. What to do is governed by IAS 8 — Accounting Policies, Changes in Accounting Estimates and Errors.
Finding examples of errors in published accounts for example or teaching purposes is not always that easy. In March 2014, Bloomberg reported an error in the financial statements of SolarCity, a large US solar energy company. The company made an error in how overhead costs were allocated between cost of sales and other expenses it seems. While overall profits/costs were not affected, the cost of sales figure increased by about $20m per annum for 2012 and 2013. You can read the full article here.