More from my dabbling with OpenLayers: I've found why the marker disappears, or at least how to keep it from disappearing. There is an undocumented parameter on the marker constructor that determines how higher zoom level the marker is displayed to. Now the map works well. A quick drawing session to create a png image of an arrow to use as the marker and it is done.
Overall the OpenLayers is very neat. It works well, there is some documentation which is readable and it is flexible and usable.
Sis now has a slippy map embedded in her prototype web site. Now if we can get the remaining 10 pages defined, written and checked we can then maybe go live.