If you used Chrome on a PC to login to Hikconnect then maybe. The username might be still be stored in a cookie.
Open Chrome, click Settings then click Advanced.
Click Site Settings:
Click Cookies:
Then click See all cookies and site data:
Then enter hik in the search field and select euauth.hik-connect.com (the prefix might be different depending on your location).
Then click the AS_LastUser cookie and the last successful username will be visible under Content.
This is may work with Firefox and other browsers too.