Read error. The system returned: 104 connection reset by peer. Why?

Question

Squid

Hello,
There is a site in the Cyrillic domain zone. For everyone (who opened it), it loads normally. Today there was a problem: a message comes from another city that they cannot open the site, the error "Reading error. The system returned: 104 connection reset by peer" comes out.
1. There is no this error in the logs.
2. On the screenshot with the error that was sent to me, the Squid logo and the admin. the email of the person who sent me the screenshot.
Do I understand correctly that the request to the site did not go through the Squid proxy? And it's not my server's fault?