lab results

I'm new here guys. I recently been working as a rehab nurse for about 5 months. I'm really worried now. Today just when shift about to end I saw a new lab result pop up on my patient access list. It was a critical lab value of 6.1 for potassium. This was the first time that I have this patient. I was freaked out! I told my charge nurse and nurse manager as well. They were totally surprise and didn't even know the lab came. They told me lab always call for critical lab values or fax over the results. They didn't received those labs through the fax machine or saw them posted to the patients charts yesterday so they didn't know about it to call the doctor. The thing was that this lab value stated that it was posted on 6/28/15 at 0000. However, the results just came up around 0530 on 6/29/2015.

I already gave the potassium 20 mEq as well as another nurse during the morning shift. I pretty sure to triple check the lab values before giving the medications and at that time around 2050 on 06/28/2015 there were no lab values for electrolytes such as sodium, and potassium. Now I find out after shift that they are ordering a stab lab to probably check out the patient potassium level. I just don't want any harm to my patient. I don't know why that lab result just pop up on the following day, but listed it for the previous day. They probably think I was careless of either not checking electrolytes labs before giving the medication or know the results but gave it anyway. I'm really freaking out.