tl;dr version: I believe I've found image evidence (and potential video evidence) of someone that matches Frank's clothing being even with the lead pack at the 10KM mat of the 2019 LAM (even though he started after them), potentially to wait in the park and then cross the 10K timing mat at the right time.
Longer version: There appear to be at least three sets of photos taken at Echo Park, where the 10K timing mat is located and a very scenic location of the marathon. The pictures all appear before the timing mat. There are four photos in question and the live video stream of the race in question. Two very close photos, 133835 and 133836, photo 200668 and the most potentially powerful photo for me was photo 452056.
In photos 133835 and 133836, you can see a figure running in the background. I wish we had the video of the spectator on the left. The clothing all seems to match. At first I thought, "Why would Frank be at Echo Park right as the Elite men came through? Shouldn't he be further down the course or back at the 5K mat?" Then I realized he would need to be there to hit the 10K mat, which is at the end of the Echo Park route which can be proven using the live stream posted by LATV, the local TV affiliate. More on that in a second.
In photo 200668, you can see a figure in the background on the right. Again, the clothing description appears to match. A high resolution photo here might prove the identify of this person.
And finally, the most interesting photo that led me to more investigation, 452056. You'll notice the figure in the background on the left, crossing the road of a marathon in clothes that also match, and again running the wrong direction, towards Echo Park and not down the road. If you were to scroll through the photos, you would see that other runner in the background with the black diagonal stripe across her shirt is Ms. Cox. An example reference photo is just a few later at 452060.
Reference photo for Cox:
This photo was taken almost immediately after the elite men went through this area. It dawned on me that there might be live stream video footage from the race stream of Frank crossing the road which would mean he was running the first 10k at faster than the winning pace to get to that point (a far stretch from the 2:21 pace that even the crazy person in this thread has claimed he ran since Barno won this race is 2:11 in a very exciting finish - you should also watch it!), and then resting for a while in Echo Park before hitting the 10K mat. Unfortunately, the video footage posted on FB is simply too grainy for me to make anything out of. However, my connection is terrible so maybe one of you can. A request may be needed to be placed with KTLA for the footage (and potential additional footage that wasn't part of the stream). You could probably even tip them off if they want to scoop the story using their own footage... The time in question on the posted live stream is 1:26:00.
I don't want to get this post deleted, so to find the stream just search "2019 LA marathon live stream." The first link is a FB live stream posted on 3/26 and is 5:41:05. The Echo Park bit starts around 1:25:00.
Sorry if someone else has already posted something similar or caught any of these pictures. I've been sitting on them for a while and haven't had time to summarize the findings until tonight or go through the entirety of this thread for a while. I'll check back maybe Monday if there are any follow up questions.
Here is a broad summary photo:
In case this is all old news and I've missed it, here are some fun photos I also noticed:
Shh, he's my bandit pacer:
I've made it through 10K! I've got all the energy in the world!
You have no idea how long it took me to find these matching arm sleeves, shorts and socks. You should see my what else I'm wearing!
My marathon sandals are acting up: