You no longer fulfill the terms of the visa, therefore it technically becomes invalid. You should also be aware that a work permit (Arbeitserlaubnis) with residency permit (Aufenthaltserlaubnis) is not a carte blanche to work anywhere, doing anything, but confines you to the town or administrative area where you are employed and is job specific to your qualifications. You can enter Germany on a 90 day tourist visa or apply for Temporary Residence Permit (Aufenthaltserlaubnis) but to look for a job you need to apply for a German job seeker's visa before you enter the country. It sounds like you have already gone through that process, so you should contact the issuing authority to clarify your position.
The EU Blue Card (Blaue Karte) is similar to the Temporary Residence Permit, but it targets a specific group of people and has longer validity. The EU Blue Card is for foreign nationals of non-EU countries who are highly skilled in a profession and want to work in Germany. Highly qualified employees have completed a higher education degree, such as a bachelor’s or a master’s degree. Those who are more likely to get the EU Blue Card have an IT or STEM background, earn €55,800 or more p.a. and are proficient in German. It is issued once you are living and working in Germany and fulfill all the (many) residency and employment requirements. It is not issued to self-employed people. No paperwork of this nature is "lost". You can refer to it in future applications, so keep it safely.