Given that there's no Zotero library data stored in Chrome, deleting cookies in Chrome definitely didn't affect your Zotero data.
If you originally used Zotero for Firefox and later switched to Zotero Standalone, it might be using a data directory within your Firefox profile directory. If you refreshed Firefox, you'd find your Zotero data in an "Old Firefox Data" folder on your desktop, and we have instructions for restoring from that. Zotero 5.0 automatically migrates data out of the Firefox profile to a "Zotero" directory in your home directory to avoid problems like this going forward.
If that's not it, you'll have to say more about what you did, because what you're describing just isn't a thing that can happen.
No Zotero library data is stored in Chrome, so what you're describing — deleting cookies in Chrome causing Zotero data to disappear — simply didn't happen. Clarifying that is not an attempt to "shame" you. If you want us to help you figure out what you did that affected your data, we're happy to do so, but you'd have to reconsider your approach here and provide more information.
Upgrade Storage
If you originally used Zotero for Firefox and later switched to Zotero Standalone, it might be using a data directory within your Firefox profile directory. If you refreshed Firefox, you'd find your Zotero data in an "Old Firefox Data" folder on your desktop, and we have instructions for restoring from that. Zotero 5.0 automatically migrates data out of the Firefox profile to a "Zotero" directory in your home directory to avoid problems like this going forward.
If that's not it, you'll have to say more about what you did, because what you're describing just isn't a thing that can happen.