Will i do appreciate you Karlie trying to find a work-around, but i think what you should say is more this:
Thank guys to have find this bug and let me validate a ETA with the dev team on when this issue will be resolve by our team. I will get back to each and everyone on this feed and let you know what will be the next steps:
1./ either fix this issue OR
2./ this is not a bug but our new way of doing things.
Shopify is a mutli billion dollars company and i think you should allow your members to have access to a road map before changes like this appers. Now we are many that did notice this change (on top of a much slower order processing btw...) and we all dislike this new reality.
Instead of convicing us on new ways to filter results, please simply get back to us with an ETA.
I'm also having this same issue but it's not with phyiscal locations and my online store. It's between my two Sales Channels. Our current process is to have two separate prefixes. One for our Web orders and one for our Amazon orders. Shopify is telling me that there is some super round-about way of making this happen. With the Order API, I would have to find all Amazon orders that come in, change the Order Name (not ID) to whatever I need it to be, resubmit the Order in the Shopify database, delete the original order. This basically creates double data though. It's completely ridiculous and messy data. I seriously cannot believe Shopify doesn't let you have separate prefixes for separate sales channels. Like someone above said, it's simple accounting that makes things a million times easier. And the fact that there hasn't been any response here from them in 2 months isn't reassuring.
We also use the order number prefix for accounting purposes (via the transactions export CSV).
I think Stephane Lafrenaye's point about clarifying the issue-- is this a bug or a feature removal? -- is on point. It can make a big difference for all of us if we hear about deprecated features beforehand, versus having the rug pulled out from under us with no notice. It's also unsettling that over the course of two months there's no straight answer about which occurred here.
On another note, the best workaround I can see for us (aiming to get the same by-channel sales information as shown on the home page in the web interface) is to do a CSV export of order details as Karlie suggested and then pull out the Location column (#54) or Device ID column (#55). Nothing in the transactions export, including the different version offered on the orders export dialog, has that information anymore now that the prefix on order numbers is gone. This is still a workaround rather than a drop-in replacement, though.
Check our invoicing app, Invoice Browse, it solves this issue, it keeps sequential invoicing numbering and different prefixes for each POS location.
Hope it helps!