Do what Wim says. That piece is called the pitman dowel. It comes out in at least three quarters of the moves I see, and most movers have no idea how to fix it. On some models you can easily slide the dowel around until it falls back in its place. For others you'll have to pull the action, which I would recommend doing for your first time anyway so that you can visualize it. Also, don't forget to adjust the pedal rods back to where they should be, since the client was messing with them.
Learning this repair is one of the easiest ways to be a superhero for your client, LOL.
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Benjamin Sanchez, RPT
Piano Technician / Artisan
(256) 947-9999
www.professional-piano-services.com------------------------------