If it is written "山田 さん は?", then it can mean "et M. Yamada?", not "et toi?".
山田 is a common Japanese surname Yamada ( 山 - やま、 mountain, 田 - だ, rice paddy ).
さん means Mr, Ms (M, Mme, Mlle), so 山田さん is Mr (or Ms). Yamada.
は is what they call the "topic marker(particle)" to start a sentence/topic, like "山田さんは 背が 高いです" (Mr Yamada is tall).
"山田さんは" by itself is rarely used, but with the "?", it can mean "What about Mr. Yamada?" or "Et M. Yamada?".
ok i wasn't sure but now i am/ Thank you :)