Head recipient area Scalp stretched by flexing forehead one day after FUE hair transplant

Bending over the reach for your vacuum cleaner seem like a normal activity.  It should not dislodge your grafts.

Based on your description it is unlikely that any damage occurred to the grafts.As long as there was no bleeding and there is no obvious change to the area everything should be fine!

It is very unlikely.  Although increased activity is not recommended initially, it is unlikely that this caused an issue.  If you were to go upside down increasing blood flow and therefore swelling to the head it could potentially pop out the follicles though.   I would take it easy for a few more days.  Best of luck,  Dr. Giordano

If you had no bleeding then you should be fine. And stick to your aftercare. One of the points must include 'do not bend down'!!
If in doubt give your hair transplant surgeon a call. 

As long as there is no bleeding after the procedure, it is unlikely you lost any tissue.  The first couple of days after the procedure is most critical, so be careful about anything touching the grafts for the next couple of days.

No, it is highly unlikely that stretching would dislodge any grafts or affect any future growth. If there was no bleeding from the area, you definitely did no harm. While in this instance you were lucky, it is important to follow post-op instructions given by your surgeon and often that restricts bending and lifting. 

Generally, unless you got bleeding, there is no harm done.  A stretching sensation can be caused by a number of factors.  Grafts dislodged immediately after surgery almost always results in bleeding however.  Its therefore unlikely that you caused any significant issues.

flexing your forehead after an FUE should never cause any problems.  The grafts become stable after a day or two