Caution: These links are graphic in some places.
https://www.ncjrs.gov/pdffiles1/nij/grants/241868.pdf
http://forbio.msu.edu/Misner et al..pdf
I was looking at these out of curiosity about the process of extracting DNA from bones. Of course, I understand about .002% of these reports. But one thing struck me, in both reports it talks about cleaning the bones and letting them dry. Which appears to take 5-6 days. One report says the process after that is quite time consuming. It makes me wonder if LE found a bone way before the major search with all of the experts. Maybe even in the fall of 2012. If the bone(s) they found were identified as Dylan's and if at that time a team of expertswere put together to develop a trajectory and then another team of experts assembled for the search. It is one scenario to explain why they searched where they did. Not in any way saying that is what happened, just thinking out loud.
moo
It seems like they might have found bone(s) on the first day of the search (the 22nd), which is what caused the search to continue. I know the actual DNA tests do not take 4-6 weeks, that is just the backlog. I also know they can do paternity testing in 2 days(different type of testing, I know). I also know that the femur is one of the best bones for getting DNA. If they also found the shoe (or something else) the same day and recognized it as one like Dylan wore, logical deduction says that they could match DNA within the four day window if they had a lab with the proper equipment and the lab was willing to put the analysis in the front of the line. But that is my opinion based on my research.
At first I was going to respond to each comment individually, but I believe that my answer responds to both AnotherSetofEyes and Ghostwheel's comments.
I am not an expert in DNA or forensic crime analysis, but I do have some experience in Forensic Genealogy and research. From what I have gathered from the PDF file listed above, is that the paper was on cleaning the bones, letting them dry and then doing an MtDNA test on the weathered bones. The order of the best results on bones tested for extraction, were the femur, rib then the pelvic bone. The paper mentioned that the reason that the femur had the highest quality of DNA extraction, was because the bone had more condensed/compact bone (not like the spongy pelvic bone) and had less of a chance of contamination. They found the Petrous (Temporal Bone) to be the best spot for DNA extraction, because of the least amount of contamination in all of the tests. Acids/PH levels of the soil, seemed to be a big destroyer of DNA evidence.
First, cleaning off the bones will get off all of the excess tissue, dirt...etc..
Using a detergent is preferable to the bleach method. Studies have shown that detergent leaves more DNA intact for extraction.
http://www.hartnell.edu/faculty/jhughey/Files/skeletalprepartionforDNAanalysis.pdf
When bones are cleaned and dried, then pieces of the bone are cut up and crushed into a powder for DNA extraction. This was a problem during 9/11, because when they found one small bone, they had to sometimes destroy the entire sample to get the DNA. The victims family sometimes received only an empty envelope that once contained the bone. They had to destroy the entire remains of the victim, to identify that individual. I am sure that in most cases that they have more bones to work with.
The paper above mentions that after cleaning the bones they try to extract the MtDNA. The MtDNA will not be unique to the individual, but most likely unique to the family. MtDNA is passed down from mothers to their daughters, then to their daughters, unchanged. Males receive this MtDNA from their mothers, but do not pass it on. So DR would have the exact same MtDNA as his mother. Finding MtDNA in the bones would help with the identification, but I am sure that further tests would have to be made to further verify his identity. MtDNA lives outside of the nucleus. If it takes 5 or 6 days to prep the bones, then it might take up to 10 days to get results back. The ultimate DNA test would be the DNA from inside the nucleus. The DNA inside the nucleus is unique to the individual. This is where Law Enforcement extracts DNA and amplifies the CODIS Markers or STRs. Some markers can be amplified in a day, most likely 48 hours if you are not on a high priority case. They have a method called PCR Amplification (Polymerase Chain Reaction). PCR method can amplify the DNA, from small samples like skin cells (touch DNA). Samples inside of the nucleus offer the best identification, but this is not always possible to get from degraded remains. Because there are more copies of MtDNA available (between 500 -1000 copies), it is easier to extract from degraded remains. There are only two copies of Nuclear DNA.
http://www.nij.gov/topics/forensics/evidence/dna/basics/analyzing.htm
http://www.fbi.gov/about-us/lab/biometric-analysis/codis/codis-and-ndis-fact-sheet