'by chance'はこちらの項目にも見つかりました。
英語の見出し語に対する説明:
bump into
- casual
- coincidental
- coincidentally
- come across
- come by
- come upon
- fluky
- fortuitous
- fortuitously
- incidental
- lottery
- nonrandom
- randomness
- run across
- run into
- stumble on