iPhone 5s fell into water, all but digitizer is working

Hi guys, I need help - my friend´s iphone fell into water, it was there for 3 seconds. She didn´t know and she only dried it and used it as usual. After a day, some problems with display occured. She let it dry in the rice, then tried it again and display works fine, but digitizer does not work at all. She gave it to me, I dried it, tried another display and everything works again. Now the question is - if everything works after 2 days of using, what is the chance that water actually got inside and damaged the logical board or anything else? Is there a chance that the only damaged part is the display?