I think you did the right thing but probably for a different reason than you think. I would suggest you get a +2 and maybe additional tests so you know when Jasper's numbers start to rise.
The reason I would have discouraged you from shooting is that you have very limited spot checks. While pre-shot tests are important with respect to whether it's safe to shoot, Lantus dosing is based on the the lowest test in the cycle. Please, for Jasper's safety, start getting spot checks during both the AM and PM cycles.
It's also very helpful if you put your cat's name in the subject line and indicate that the 104 is your PMPS.
you can get back on track with your regular shot time tomorrow morning. good for you for getting that +4 - as you get more spot checks it will help tell more about how jasper's body is responding to this dose.