I suspect this is a reference to the specific feature infinite/virtual scroll. The DOM nodes are only materialized when you scroll near them. CTRL-F is not able to find text that isn't currently in the DOM. If you scroll it into view, it suddenly starts working.
That's a very far stretch from purely the topic "Virtual DOM" though, no matter how few JS knowledge.
I hate Infinite Scroll with a passion. FWIW Infinite Scroll can be and is often implemented as a jQuery plugin.
