Both are wrong. You use since when talking about a specific point in time. (I suppose you could use from in this case as well, but I haven't seen it in actual American usage.) For example:

When you returned, I had been home since 3:00.

When talking about a duration, for is used:

When you returned, I had been home for 10 minutes.

Both are wrong. You use since when talking about a specific point in time. (I suppose you could use from in this case as well, but I haven't seen it in actual American usage.) For example:

When you returned, I had been home since 3:00.

When talking about a duration, for is used:

When you returned, I had been home for 10 minutes.

Both are wrong. You use since when talking about a specific point in time. (I suppose you could use from in this case as well, but I haven't seen it in actual American usage.) For example:

When you returned, I had been home since 3:00.

When talking about a duration, for is used:

When you returned, I had been home for 10 minutes.  

Both are wrong. You use since when talking about a specific point in time. (I suppose you could use from in this case as well, but I haven't seen it in actual American usage.) For example:

When you returned, I had been home since 3:00.

When talking about a duration, for is used:

When you returned, I had been home for 10 minutes.