(Note: This situation/problem appears to have been resolved when running Logic Pro X 10.2.1 or higher. See this
for further information.)
When you run TouchOSC on an iPhone or iPod touch, Logic uses different control surface settings than when lpTouch is used. Logic will ask you to add your iDevice twice, once when you run TouchOSC, and once when you run lpTouch. If you clicked "Add" each time then you end up with Logic having two OSC control surfaces registered, but to the same device. This situation works very erratically under the best of cases but in this particular case the most likely result is that lpTouch is completely unresponsive and does not receive valid data from Logic.
On the other hand if you did not click "Add" for the second popup then Logic is using the wrong settings. For example, if you first ran TouchOSC, then run lpTouch, but do not add your iDevice a second time, then Logic uses the wrong settings for lpTouch. When you run TouchOSC though it works properly. Likewise if you first ran lpTouch, and then switched to TouchOSC, then TouchOSC works improperly.
The solution in all cases is that you must remove the previous OSC device setting from Logic's control surface setup before you switch to the other app. Furthermore you must exit Logic after removing the first, then restart Logic. Otherwise Logic may operate the new control surface in an unreliable fashion. See #9 for more information about managing Logic's OSC control surface setup.