You did not "see" a spike for several reasons.
the first is that you did not exceed the capacity of the biological filter. This is the bacteria on your LR. In normal cycling situations, there is no biological filter, and it must grow. The ammonia is food for that bacteria, but there is a lag time for it to grow, which results in the first "spike" of ammonia. This happens if you have uncured LR (die off produces ammonia), if you overfeed the tank or use shrimp (the rotting produces ammonia) or if you put fish in (the food plus waste produces ammonia).
If you have cured LR, then you can get away with livestock and the bacterial capacity is sufficient to carry the bioload. this is what probably happened in your case.
Nitrite spikes follow after the ammonia spike as another type of bacteria grows in...again, you had this. I would expect to see some degree of nitrate. However, algae often can use this. Our test kits are also not particularly accurate (what kind do you use?). Nitrate test kits are usually a bit finicky and so it is possible you are not registering nitrate due to a test kit issue, or that it is just too low and being used by the algae.
Regardless of the strong opinions on it, there are many ways to successfully cycle a tank. I am not a fan of damsel cycling, but it does work. However, you did not do a damselfish cycling, IMO.
Another form of cycling a tank is effectively using an established biomedia and very slowly increasing the bioload. You should be aware that you could at some point overwhelm your biofilter in the early stages because you probably did not "push" the tank. A whole rotting shrimp puts a lot of ammonia in the system, effectively providing the system with a "worst case scenario." Old school damsel cycling used 1 damsel per 5 gallons, and they were fed heavily. Dead fish were left in the tank. This is a harsh, extremely nasty soup but it is nonethless a very hard cycle to the tank.
I suspect you are relatively safe but I would not go crazy adding fish quickly. I generally prefer a form of "hard cycle" but that is me. There is the possibility that for some reason you have just not measured this yet, and you are on the edge of it.
The algae could also be a circulation issue in some cases so ensure that is addressed if need be. I would feel better seeing some nitrate, as mentioned. I would suggest in a week or two, a more robust clean up crew would be the way to go. Have you done a water change?
