It is possible that Methusaleh died in the flood, but I don't get that sense.
The eisegesis/exegesis discussion doesn't always do justice to a bible passage.
At some points I'm more in favor of a direct evidence/circumstantial evidence approach. There might not always be enough evidence to convict, but there's more than enough to be suspicious.
The problem always seems to be in having your hearers understand that you're speculating about things you suspect rather than stating affirmatively the things about which you are sure.