In this case, you would use a Status/Show query, like this in v2.1:
var friendTweets =
from tweet in twitterCtx.Status
where tweet.Type == StatusType.Show &&
tweet.ID == Id
select tweet;
or this in v3.0:
var friendTweets =
await
(from tweet in twitterCtx.Status
where tweet.Type == StatusType.Show &&
tweet.ID == Id
select tweet)
.FirstOrDefaultAsync();
The reason you received a Page does not exist because your query was for a user with that ID and that user doesn't exist. Here's the documentation for this query: