My grandson's Maunsell HO derailed due to a piece of unstable track (Major Gramma fail!). In the process, the tender separated from the engine. I cannot figure out how to reattach the tender. No pieces appear to be broken, there is a small hole where a "coupler" may have been. The tender "coupler" is a "Y" shape with a tiny piece sticking up at the end of each "Y".  I'm not able to upload a pic right now. Does anyone out there have this engine and tender that will post a picture of the back end of the engine so that I may see exactly what I need to find? Thank you so much for your help.

Updated

EDITED:

When I try to connect a green extension wire to a turnout, the plugs do not meet completely (i.e., the prongs can still be seen)? Is this normal?  Is it safe to run under our table covering? Links to photos follow.

Please keep in mind this is a set-up for a 5 yo, high-functioning, autistic young man. He received his first Bachmann starter set a year ago and treats his trains with respect and care. It is my first experience with trains as well. Your help is much appreciated.

Thanks.
https://photos.app.goo.gl/hV59SzWx3eaPkPTk8
https://photos.app.goo.gl/ZA2EiRKLCjHpSnPY9]