I have no idea why someone would tell you that top bar hives will not work in Colorado. It bothers me when a proponent of one type of hive will tell you that another type of hive won't work when they haven't used they type they are discrediting.
Anyway, I have been using top bar hives for many years here in Colorado and they work just fine. I have just warre hives now but had horizontal top bar hives earlier. The flow is just fine here to support any type of hive. If you are using a horizontal hive the main thing to be aware of is when the heavy flows occur and to keep enough space in the hive to reduce swarming while at the same time leaving enough honey for the winter.
I have used langstroth, htbh and warres and they each have advantages and disadvantages. As far as your issue, I don't think it has anything to do with the type of hive you have. It's really difficult to give you a specific reason for their leaving without some backround information. Where did you get the package and how long had they been with the new queen? Are you using a brand new hive or is it used? Did you restrict the entrance when you hived the bees? Where is the hive located? Do you have any pictures?
Sorry about the 20 questions but there are some things that tend to cause a greater likelyhood of leaving the hive. If it's a new hive in that it has never been used I recommend putting a drop of lemongrass oil in the hive as well as rubbing some beeswax on the inside. That tends to help it feel more natural for the bees and they tend to stay better if done. Restricting the entrance down to one to two bees in size will help two things. It limits the potential for robbing by another colony and it also makes it more difficult for the bees to abscond. If the package hasn't been with the queen for 3-4 days they are more likely to leave. I have gotten into the practice of keeping my bees in my garage for 2-3 extra days before hiving them. That seems to help them be used to eachother and have a greater desire to stay as well as accept the new queen.
Hive location is another consideration. If the hive is in direct sunlight for most of the day the bees won't be as happy as if it is shaded from the hot afternoon sun. I have also had better luck when I orient the hive so the bars are running north/south rather than east/west. These are just a few of the things that can make a difference in the bees staying or leaving. To be completely honest, there is nothing you can do to guarantee that they will stay. Trying the above mentioned items has helped mine to stay but they still have a mind of their own and could still leave.
Don't give up. I would get on a swarm list and see if you can get a swarm that way. You may also call some local exterminators and request that they call you if the encounter a swarm. If you do a package next year, go with a local company. I highly recommend highland honey. They have really nice stock and their prices are better then most.
Feel free to drop me a note and you are more then welcome to come by and see the hive I have in my backyard if you are in the Denver area. I have other hives at other locations as well. I am also happy to come by and take a look at your hive and see if I notice anything out of the ordinary. Best of luck!