Accidentally strained 11 days post facelift, advice?

Hi there and thanks for your question.  The biggest worry with any injury after a facelift is a hematoma, which is a collection of blood under the skin.  In this case, the blood may need to be drained from the face.  However, after 11 days everything should be healing nicely.  If you see or feel any changes, I suggest following up with your plastic surgeon.  Best of luck and feel better! 

Your facelift should be quite durable by now. I suggest you take a close look at your skin. Are there any new areas of swelling. Any new bleeding or bruises? Any areas that concern you?
The facelift is probably ok if there are no signs of hematoma or suture breakdown.
A quick examination by your plastic surgeon will clarify any questionable areas. 

From your description of the straining event you had 11 days after your facelift, I doubt that any damage was done.  If you are feeling fine and there was no worsening in your appearance, you should be fine.