I have only had two Chase shops go sideways on me... Once, I had to wait thirty minutes, but that did not bother me as there was a huge rush of customers and the bank was completely swamped.... The two that went sideways? They had hefty bonuses and were a three hour drive (each way) from home - at least they were in the same town on the same trip. Unfortunately, neither had a banker available at all that day. I was not going to make a second trip out for these shops - they were only worth the time because I had several other nice bonuses that day. I attempted to email and contact the MSP, but got no response. I ended up returning home with proof of visits (GeoVerify, photographs, business card, product folder), but could not actually do the shop. I went around a few times with various folks at the MSP, but eventually did get paid - two days ago.
My impression is that if you are polite, articulate, reasonable, and do good work, the MSP wants to work with you and will give you some concessions. In my case, I had made a seven hour round trip for what had to be a drop-in visit and, through zero fault of my own, could not complete the shop.
I don't know if they will view the shorter trip the same way. However, I agree with the previous comment that it might be worth while to agree to do the shop on a different day and ask for a bonus.
Hard work builds character and homework is good for your soul.