With a quick search of the web I found what might be some useful info for you, especially in the second link, a PLR that has relevant code sections, that would be a place for you to start for further research:
some general information from SEC on how long the states hold securities, in general: https://www.sec.gov/fast-answers/answersescheathtm.html
and this 2009 PLR where the IRS ruled that the taxpayer was allowed to defer gain or income recognition by purchasing replacement securities using the escheat funds (proceeds) received from the state. https://www.irs.gov/pub/irs-wd/0946006.pdf
Hope this helps you some.