If the Infinite scroll is not implemented in search engine friendly way, crawlers find it difficult to crawl & index. Then the content will not surface in search results. Google Webmaster Central has a great article on how to implement the Infinite Scroll in a search engine friendly way.
1) The webpage or the CMS used should produce a paginated series to go along with the infinite scroll.
2) All the individual items are accessible. However, with the normal infinite scroll, crawler can’t discover individual items displayed after the initial page load.
3) Decide how much content to have in each page.
4) The content should be so divided that there is no overlap.
5) Each component page contains a full URL.
6) Use rel=next and rel=prev values in the section to configure pagination.
7) Implement replaceState/pushState on the infinite scroll page.