Why didn't the Keystone (Mill Gulch) bridge end up in Denver?

Not long ago, I posted a video (see below) showing the former South Park Keystone Bridge (also known as Mill Gulch Bridge) in Helen McGraw Tatum Memorial Park in Bailey, Colorado.  I found a little more background on why it didn't end up in Denver as planned (as discussed in this 1977 Rocky Mountain Rail Report).  The information came from pages 393 and 396 of The Mineral Belt Vol II -- Old South Park -- Across the Great Divide published in 1978 by David S. Digerness

"The road below the dam would make one crossing of the South Platte River at the location of the existing narrow-gauge railway bridge at Keystone.  That structure will be replaced with a steel-beam concrete-deck bridge, with a 22-foot running surface employing the existing bridge abutments.  It is planned that the historic Keystone bridge will be carefully dismantled, and each piece will be marked and stored at Kassler for future use whenever an appropriate site is located.

"It is interesting to note that the Keystone bridge was offered to the City and County of Denver by the Denver Water Board in the fall of 1977.  The bridge was to have been used as a pedestrian crossing on the South Platte River in the city – positioned so that the Auraria campus parking lot could have been used for public parking during Bronco football games.  However, the U.S. Bureau of Land Management (BLM) stepped in and said the bridge belonged to them and the Denver Water Board could not give it away because they did not own it.  It seems that when the railway abandoned their right-of-way, the bridge was left behind – and bridge, right-of-way and all reverted back to public domain administered by the BLM."

Some other info on the process of dismantling the bridge in 1978 can be found here from the Rocky Mountain Rail Report.