It happens sometimes for any number of reasons. At GE people wrote 'see you soon! :)' on a co-worker's retirement card because retirees typically would return as a contractor doing the exact same job.

Perhaps less common, Larry David rage quit his writing job at SNL on Saturday and returned to the office Monday like nothing happened [0].

[0] https://www.vanityfair.com/news/2017/10/larry-david-re-enact...